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FIREFLIES Firefly Notebooks by Terry Lynch Terry Lynch with the Firefly Notebooks Techniques with respect to the collection, observation and rearing of the firefly P. pyralis and Photuris with notes upon the feeding behavior of Photinid and Photuris larvae and the implications these contrasting behaviors have on evolution of the species in fireflies. Introduction Between 1968-75 I kept a series of notebooks to record my observations, experiments and reflections with respect to fireflies, primarily the species Photinus pyralis. I have made additional studies of flies, aphids, crickets, cockroaches and other insects over the years (1968-2000) and read widely with respect to insect behavior. Hence I have gleamed a good understanding of these marvelous creatures and would now like to take the opportunity to publish some of my observations for the benefit of others who may be interested in following up on these studies. I will initially concern myself with the firefly notebooks I maintained during the early 1970's (my studies in 1968 and 1969 related primarily to adult P. pyralis, its flight and mating behavior and were recorded on loose leaf paper in several notebooks). These are a set of six paper bound composition books manufactured by various companies. I will refer to the books as follows: Book 1 - July 19, 1970-Jan. 14, 1971 Blue Horse #3997 composition book 24.5cm x 19.5cm Book 2 - April 28,1970-June 17, 1970 Square Deal composition book 24.5cm x 19.5cm Book 3 - June 17, 1970-July 4, 1970 Square Deal composition book 24.5cm x 19.5cm Book 4 - Jan. 15, 1971-April 2, 1971 Blue Horse #3997 composition book 24.5cm x 19.5cm Book 5 - May 19, 1971-Aug 6, 1971 Tulip composition book 9 5/8" x 7 1/2" Book 6 - Jan. 30, 1972-May 19, 1975 Boorum & Pease #705 record book 19.2cm x 12.1cm The mentioned observations in the later notebook filled the first one-half of the booklet. To illustrate the nature of these firefly notebooks, I have produced scanned images of pages which illustrate methods, techniques and designs used or invisioned. Please refer to these figures which are presented in their raw form to give one a better feel for how the naturalist works: Figures and Illustrations Firefly eggs: Collection in Petri dishes Egg collection in Petri dishes Egg collection/rearing cage design considerations Three types of P. pyralis larvae hairs observed Anal appendage of P. pyralis larvae illustrated P. pyralis larvae antennae illustrated Antennae of P. pyralis illustrated Grooved tooth of P. pyrlais larvae Soil sorting techniques for firefly larvae collection Collection of Photuris eggs in bottles Field station three on University of Florida campus map Observations of Photinid larvae in rearing chamber Rearing chamber for Photinid larvae Mass rearing cages for Photinid larvae Photomicrographs and document production Additional records were maintained which included tape recordings, photographs, drawings and field notes. Also I made a number of photomicrographs of all body parts of I-instar P. pyralis firefly larvae which I believe may be the first such photographs of a I-instar firefly larvae ever made, given that I am reasonably certain no one else ever bothered to play mother firefly to P. pyralis prior to my work done in 1970.. Also photomicrographs were made of all body parts of I-instar Photuris larvae. Photomicrographs were made using a Lafayette microscope Model 99-7039WX with a 35mm Canon single reflex camera attached to the microscope with an adapter. All photos were made using Kodak Plus-X panochromatic 100 ASA film. Exposers were made using a cable release with the camera's exposure meter set to enable the automatic timer function. Scale was determined using a Edmund Scientific Co. graduated ruler accurate to 0.01mm. The diameter of the microscope's actual projected field was measured against this ruler and compared with photograph enlargements to obtain a true and accurate measure of the firefly larvae photographed. Digital images were prepared from photographic prints using a Hewlett Packard ScanJet 5200C. Then images were cropped, edited and composed using Photo Suite III, being careful to not add any significant distortion and accurately configure the scale against the original photographs (digital imaging software permits distortion of images in both the horizontal and vertical plane when images are resized). Hotdog Professional 5 HTML editor was used to prepare this document for publication and presentation on the Internet. A QuickCam by Logitech was used to product the colored photo of the author with the firefly notebooks. Figure 1. I-instar P. pyralis larvae at 50X taken 24 July 1970. Note body is narrow and elongated, an anatomical feature characteristic of a burrowing larvae. Also legs are fitted with sharp claws which may aid in holding prey. Anal appendage (not shown) also is covered with many tiny hook like hairs which aid the larvae in attaching itself to surfaces which may include its prey. From my first observations of Photinid and Photuris larvae I wondered what the significance may be of the fact Photuris has a toothed mandible while P. pyralis has a toothless mandible. This significance later became apparent after I labored many hours rearing these larvae, collecting larvae in the field and observing the feeding behavior of firefly larvae. Figure 2. I-instar P. pyralis larvae at 200X taken 24 July 1970 showing toothless mandible and mouth parts Note that the grooved toothless mandibles are used to inject prey with a strong digestive enzyme. Also there is not the same obvious thick tuff of mandibular hairs around the mouth parts as in Photuris larvae. This is because P. pyralis larvae eat their prey alive, using its grooved mandibles to inject digestive enzymes into prey, turning the living prey into a liquefied mass of proteins. Once its prey is liquefied P. pyralis larvae then devours its prey by drinking the liquefied tissue. Figure 3. I-instar P. pyralis larvae at 200X taken 24 July 1970 showing toothless mandible and antennae. The larvae may use its antennae to sense its primary prey, earthworms, which it attacks and devours. Observations and facts Observations will be reported as enumerated or dated facts. Conjectures, theories or questions for further study and research will be noted as such. When I add new thoughts, ideas or conclusions not in my original notebooks and these will be noted as an update or addendum. In regard to these firefly observations it should be noted that the following facts were established: 1. Photinus pyralis adults exhibit two distinct types of preflight behavior, what I have called a rest position and an alert position. In the rest position males become active at twilight and climb up upon a plant stem or leaf and appear to rest with their heads and antennae down. They remain in this rest position for many minutes. Then when the light intensity diminishes the males appear to peak up, raising their heads and wiggling their antennae. At this point the males will respond and fly in response to the blink of another male firefly. Males in this alert position may also be induced to fly by blinking a pen light to mimic the flash of another male firefly. Some time after I first reported this observation John Bonner Buck noted the behavior in other species of fireflies. I had occasion to meet with Dr. John Bonner Buck at the National Institutes of Health in Bethesda, Maryland so he was well aware of my work with fireflies. Dr. Buck was very cordial and showed me some railroad worms he had been sent from a colleague. I was much surprised years later to read an article by him in Scientific American mentioning the two preflight positions of Photinids and not crediting me with having first made this observation in P. pyralis. 2. Adult P. pyralis may have their life span increased by feeding them honey water in captivity. This is useful when attempting to rear fireflies as it may be helpful to extend the life span of adults while endeavoring to collect eggs. 3. The larvae of P. pyralis may be readily obtained by collecting adult males and females in the field. Adult males are easily captured in an insect net as they conduct their mating flights. Females can be located with a pen light by mimicking the flash of a male firefly. To collect eggs place male and female fireflies in containers with moist paper towel or moist sterilized soil. I generally used Petri dishes, baby food jars or terrariums for this purpose. Female fireflies will deposit their eggs which will then harden into tiny, glassine pearls. When first deposited these eggs are very fragile and may be handled by washing them into a dish with water. Use an eye dropper to pick up firefly eggs and transfer them to sterile paper towel, filter paper or similar substrate set inside Petri dishes or baby food jars. When air dried firefly eggs harden and can be very gently handled without breaking the egg shells. The following is from Firefly Notebook #2 made in Jacksonville, Alabama: June 8, 1970 - Firefly Eggs: (See: Firefly eggs: Collection in Petri dishes ) Nine Petri dishes were washed with hot soapy water. Into each Petri dish was places a female P. pyralis fireflies copulated with a male, or a female and several males were added. In one dish two females were place. The Petri dishes were sat in a large glass cookie jar. The inside of the cookie jar was lined with moist paper towel and on the bottom of the jar were sat moist sponges. The top of the jar was covered with moist cloth and metal lid. Thus the Petri dishes were contained in a moisture chamber. Inside each Petri dish was places a small drop of honey. Will fireflies lay eggs in the Petri dishes? Will moisture (a humid environment) keep fireflies alive? Will mold grow on the eggs? Will larvae hatch? Are eggs luminescent? Do fireflies eat honey? ADDENDUM: The later fact was confirmed in observations I had made earlier in May 1970; ie, adult fireflies will eat honey. What I was really trying to establish is a way to keep adult fireflies alive so they would deposit a maximum number of eggs. I found that adult fireflies will eat honey and this does extend their life span. However, the best way to induce egg laying is to maintain females in a terrarium with soil. June 13, 1970 - Eggs laid by Photuris captured in Alexandria, Virginia were observed in a dark room and found to glow faintly. The eggs appear as small yellow spherical bodies about one millimeter in diameter. The eggs are hard and when placed on glass roll. The eggs bounce when they fall on paper making a slight sound when hitting the paper. June 12, 1970 - 76 male P. pyralis fireflies were captured this evening. I purposefully did not catch more male fireflies as I was searching for females of which 22 were captured, some which have extremely large abdomens. June 16, 1970 - Egg collection: Male and female P. pyralis were placed in a 2 gallon terrarium. These fireflies were captured June 14, 1970. Twenty-nine females captured on the evening of June 15 were added to the terrarium. The terrarium now contains a total to 49 females P. pyralis. ADDENDUM: During this period I was also studying various aspects of adult P. pyralis including how to maintain adults for rearing and egg collection as well as adult behavior. I built a number of rearing cages and terrariums plus kept fireflies in jars and Petri dishes. Often females would deposit eggs. I even experimented to see if eggs removed from a female by mashing her abdomen would hatch. They were infertile, usually rotted and did not hatch. Also I found that adult P. pyralis would drink honey water which extended their life span. Hence feeding adults honey water would enable them to be kept alive so that they may mate and deposit a maximum number of eggs. June 18, 1970 - Procedure for collecting, handling and hatching firefly eggs. Place male and female fireflies in a Petri dish with moist paper towel during the evening. In the morning remove the paper towel from the Petri dish and place the paper towel in a bowl of water. Any eggs on the paper towel can be washed off by squirting a stream of water across the eggs with an eye dropper. Eggs can then be picked up with the eye dropper and squirted out of the eye dropper onto a moist piece of paper towel. Any eggs deposited upon the glass of the Petri dish are removed by placing water in the Petri dish and soaking the eggs until they no longer adhere to the Petri dish. Eggs are always picked up in a drop of water as eggs are very fragile and handling with a camels hair brush or dissecting needle will damage egg. Each day eggs should be washed off of the moist paper towel which is kept in an autoclaved Petri dish, and collected in a Petri dish of water. Eggs are removed from the Petri dish and replaced upon a fresh moist paper towel. The purpose of this procedure is to prevent eggs from becoming molded or mildewed which will happen if eggs are kept upon the same moist paper towel for several days. By washing eggs daily fungus is prevented from growing upon the eggs, and by placing eggs upon a fresh moist paper towel, fungus growing on the old paper towel is disposed of. No fungus should occur upon eggs even when kept in total darkness twenty four hours per day but if eggs themselves appear to discolor or be attacked by mold, then the eggs may be exposed to 12 hours of daylight. Eggs should be observed daily for hatching. When larvae hatch they should be handled in water drops just like eggs. Larvae may be fed sterilized animal meat. (To place eggs on a new moist paper towel simply wash the eggs off the old paper towel on to a new dry paper towel. The wash water will wet the new paper towel. This procedure may be repeated to insure final paper towel contains only clean water). ADDENDUM: These initial methods used to handle firefly eggs are sound. However, in working with firefly eggs I learned that it is best to allow them to air dry to the point that they are firm, hardened and resemble tiny pearls. If the eggs are kept too wet they may become susceptible to mold or rot. In my early work I was not handling the eggs in a sterile environment nor always allowing eggs to sufficiently dry. This is why mold or rot was sometimes observed. A better method is to use water only as an initial aid in collecting, handling and sorting firefly eggs. Then set the eggs on sterile filter paper or gauze to dry and set the sterile filter paper or gauze inside a glass Petri dish or baby food jar with only a tiny amount of moisten substrate to avoid desiccation of the eggs. Firefly eggs, when hardened and kept in a moist environment, are durable little egg cases, which can roll, bounce and endure gentle handling. Problems arise when the eggs are not allowed to dry such that a film or water remains upon the eggs allowing bacteria or mold to infect the eggs. However, when the egg shells are allowed to harden, their shell protects them from rot. June 19, 1970 - Eggs of P. pyralis were observed in complete darkness and found to glow with a faint green light. Eggs had been collected June 18 from females which laid the eggs on moist paper towel in a jar. Eggs were washed off of the paper towel and placed on a moist piece of paper towel in a Petri dish. June 21, 1970 - Techniques for handling firefly eggs. To remove eggs from moist paper towel wash the eggs off of the paper towel with a fine jet stream of water. This may be obtained using a gallon jug elevated four feet above the work area, siphoning water through a glass, rubber tubing and clamp arrangement. Wash eggs into a bowl and separate individual eggs from debris (firefly legs, antennae, pieces of paper towel, etc.) with an eye dropper. Place eggs upon a moist paper towel with an eye dropper. Each one or two days wash eggs from paper towel with a jet stream of water. Collect eggs in small plastic 30 ml. cups (A type of cup made by Thunderbird Corp., El Paso TX). Wash eggs in running water for 5-10 minutes. Let eggs settle into bottom of cup and pour off water being careful not to let eggs run out of cup with water. Hold cup upside down over a piece of paper towel (small folded paper towel squares) and with as little wastes as possible wash eggs onto paper towel. (All paper towel squares are sterilized in boiling water prior to usage, letting cool inside the boiling pan). Replace paper towel with eggs in Petri dish. Cover Petri dish. ADDENDUM: In these early studies I was interested in collecting firefly eggs so that I could observe them and study the emerging larvae. However handling eggs in this manner may actually reduce yield. A better method is to simply allow adult female to deposit eggs in soil, then collect the soil and allow eggs to incubate and hatch in the soil. The tiny larvae which hatch may then be observed. They may be picked up and handled very gently using a small red sable artist's brush. P. pyralis larvae turn grey after hatching from eggs and are well camouflaged against dark soil or leaf litter. Also P. pyralis larvae burrow into soil so this may make them difficult to locate. However they can be spotted using a magnifying glass. I recommend providing young P. pyralis hatched in soil with a diet of freshly killed adult fruit flies or fruit fly larvae. June 24, 1970 - At 04:35 hrs. females inside the terrarium can be seen depositing eggs in soil. The females press their abdomens into crevices in the soil and their deposit their eggs. One female is seen sticking its abdomen into a small hole in the soil and there apparently laying eggs. Upon the surface of the soil can be seen small clumps of eggs. June 30, 1970 - Approximately fifty eggs were collected by washing a tablespoon of soil taken from the terrarium in which male and female fireflies had been kept. Collecting eggs from a terrarium with a soil bottom thus seems to be a good collection technique. July 1, 1970 - An estimated 160 eggs have been collected by letting female P. pyralis deposit eggs in bottles (upon moist paper towel), then working daily to collect eggs (See Egg collection in Petri dishes ). In contrast I collected over 200 fertilized eggs from the terrarium. Terrarium collection thus appears more suitable than does collection of eggs from individual females in bottles. Eggs collected from the terrarium are not molded and have hardened shells and are therefore more resistant to mold than eggs not laid in soil. Resistance to mold seems to be the result of eggs hardening their covers. For eggs to harden their covers they must be kept in only a slightly moist environment. I have found that eggs kept upon small netted cloth like mosquito netting are easy to wash, the water drying off the eggs quickly so that eggs are not water soaked. Eggs can then be laid in a Petri dish or baby food jar while still upon the netting. The Petri dish contains clean moist paper towel to provide a humid environment but the eggs are not in direct contact with the moist paper towel so their shell can harden. With eggs upon netting daily washing is greatly simplified. Simply remove the netting, hold netting over a cup, and rinse eggs with a jet stream of water. Replace moist paper towel each few days to avoid mold formation. July 3, 1970 - An estimated 150 eggs were collected from the terrarium in about two hours work separating the eggs from the soil. In view of the number of perfectly good, hardened, durable eggs collected, the use of terrariums should be a standard procedure in collection of firefly eggs. Terrariums should be large and covered with a soil bottom. Only the upper one-half inch of soil need be checked for firefly eggs, but a deep layer of soil will insure moisture fro the fireflies to lay their eggs. July 3, 1970 02:20 hrs - Four P. pyralis larvae have hatched from eggs. The larvae, freshly hatched, appear white with black eyes and small red mouthparts. Larvae appear longer than Photuris larvae. ADDENDUM: I had earlier in June of 1970 hatched Photuris larvae from eggs collected from a large female. At the same time I was endeavoring to collect eggs and rear P. pyralis from specimens collected at my home in Jacksonville, Alabama. I used a variety of different rearing cages and terrariums to collect eggs from large female P. pyralis. (See Egg collection/rearing cage design considerations ). July 3, 1970 - A freshly hatched P. pyralis larvae measures about 3.5mm. One of the two larvae has turned slightly gray. The larvae resemble small counterparts of larger, later instar larvae. These larvae hatched 15 days after collection of eggs. (No mold has yet occurred upon paper towel boiled and placed in Petri dishes June 18, 1970 when these eggs were collected. Thus this method of collecting P. pyralis eggs and hatching them upon sterile moist paper towel or substrate seems effective. 4. Once eggs of P. pyralis are collected they may be easily maintained in Petri dishes with moist, sterile paper towel, filter paper or other substrate. The eggs themselves should not be allowed to remain in contact with fluid or they will not harden and may become susceptible to rot by fungus or bacteria. When firefly eggs are properly dried they will appear as small pearls which can roll around inside a glass Petri dish. These eggs take 14-16 days to incubate and hatch. Prior to hatching the larvae inside the eggs will respond to vibrations (gently tapping the Petri dish) by glowing brightly. This is an indication that the larvae are almost fully developed and ready to hatch. 5. I-instar larvae of P. pyralis are very exciting to observe. They exhibit several notable features: an anal appendage which consists of finger like tubes that are covered with small hooked hairs; a pair of grooved mandibles which enables the larvae to inject digestive fluid into their pray and dissolve the flesh of the pray, turning flesh to liquid which the larvae then ingests; and the most predominate feature is a pair of lanterns which glow most brightly when the larvae is disturbed after a period of rest. I-instar larvae of P. pyralis lend themselves to microscopic examination, since they are flat, thin and translucent when they first emerge from their eggs. This is an excellent time to photograph the larvae and to observe their internal anatomy. The following is from Firefly Notebook #2 made in Jacksonville, Alabama: July 3, 1970 - Photinus pyralis eggs collected from the terrarium were taken into a dark room. The eggs in a Petri dish were laid upon the top of a counter and as my eyes adjusted to the darkness I saw a faint dim glowing inside the Petri dish. Removing the Petri dish's cover I observed the eggs with a 10X lens and was able to see the individual eggs glowing. I replaced the top of the Petri dish to leave the room and then noticed two bright spots on opposite sides of the Petri dish. These spots were glowing brighter than the other eggs. I sat the Petri dish down on the counter and looked at these spots closer with my magnifying glass. Each bright spot was a larvae inside the egg glowing. I hit the counter top and sent vibrations through the Petri dish and as I watched the eggs lit up brighter and brighter. The more I hit the counter top the more eggs that lit and the brighter the glow grew. Thus vibrations appear to alarm the developing larvae and cause them to glow inside the eggs. The eggs which glow brightly, with a glow so bright that it can be seen in a dimly lit room, contain larvae about ready to emerge from their eggs. Thus, eggs containing almost mature larvae can be separated from eggs containing less mature larvae simply by the brightness of glow induced by vibrations. It may be that a bright glow occurring when larvae in eggs are alarmed serves to ward off enemies. The following is from Firefly Notebook #1 made in Jacksonville, Alabama: July 19, 1970 - P. pyralis larvae. Of the fifty larvae collected July 17, 1970 and placed in sifted relatively dry soil, the larvae can be seen some to have burrowed 1cm. into the soil (as deep as the soil is) and some to be crawling about on top of the soil. The relatively dry soil does not seem to harm larvae; ie, does not seem to dry larvae out. These larvae are being kept in baby food jars with a cloth top. Such a top prevents condensation from building up in the jar. Fifty drops of water were added to the soil. One apparently desiccated larvae was found in the relatively dry soil of the baby food jar from July 17, 1970 which contained 42 larvae. This observation indicates larvae may require more moist soil than is contained in the jar. July 29, 1970 - Tally of P. pyralis larvae collection from eggs: Larvae collected before July 17 = 812. Larvae collected July 23 = 33. Larvae collected July 29 = 71. A total of 916 P. pyralis larvae have been collected! ADDENDUM: From the many P. pyralis larvae that I was able to hatch from eggs in the summer of 1970, I was able to study their behavior and anatomy. However I did not discover that Photinid larvae eat fruit flies until I moved to Gainesville, Florida and began collecting and observing larvae in the field during the winter and spring of 1971. (See Field station three on University of Florida campus map ). Hence none of the I-instar P. pyralis that I reared in 1970 survived beyond their first instar. Aug. 15, 1970 17:50 Photinid larvae collection in the field (From Jacksonville, Alabama). A Photinid larvae was found by examining soil taken from a pine forest wooded area. The soil was examined in a dark room. The larvae glowed very brightly when touched and handled but its bright glow lasted only briefly, about a second. Then the larvae glowed dimly. This bright glow reaction to tactile stimuli may be needed to ward off enemies. The larvae was examined and it did not crawl or walk about but only moved flexing its abdomen back and forth. Perhaps the larvae was injured while handling. The larvae should retain its ability to walk about, for a similar very large Photinid larvae which I found in Virginia was able to walk about easily. The larvae appeared a dark gray. ADDENDUM: This larvae was carefully examined under the microscope to learn its anatomy. I made drawings of its antenna with hair structure (See Three types of P. pyralis larvae hairs observed ), grooved mandibles (See Grooved tooth of P. pyrlais larvae ) and anal appendage (See: Anal appendage of P. pyralis larvae illustrated ). I also observed I-instar P. pyralis and made photomicrographs of I-instar P. pyralis larvae. Sept. 26, 1970 - Larvae collection, Jacksonville, AL. From a wooded area soil was dug at 00:01hrs. The soil was inspected in a dark room for larvae. A bright speck of light was seen in the sandy, barely moist soil (soil felt moist, not damp but cool moist). I grabbed the speck of light and placed it in a plastic container. The contents of the plastic container (soil and debris was places in a Petri dish. A paper towel moisten with diethel ether was placed in the dish. After about a minute a glow was seen. The glow was isolated from the soil and when a flash light was shone upon the glow I found a 5mm long firefly larvae. The larvae was allowed to recover from the initial ether treatment. Then the larvae was placed in a Petri dish by itself. Returning to a dark room, and allowing my eyes to grow use to the lack of light, I observed that the larvae was not glowing. Ether was places upon a paper towel and put in the Petri dish. After about a minute the larvae began to glow continuously as a small point of light. These observations indicate that firefly larvae glow continuously when etherized. Larvae normally may glow only very briefly when first located, but etherizing the larvae makes them glow for several minutes permitting the larvae to be easily removed from debris. As etherized larvae glow continuously and brightly a method has been found for separating larvae from large amounts of soil. Place larvae containing soil in a large flat tray (as a film developing tray or glass Pyrex baking dish). Spread the soil thinly over the bottom of the tray (about 1/4" deep), place an ether soaked paper towel in the tray, and cover the tray with a piece of glass. All larvae in the soil will be made to glow continuously and can be picked out and removed from the soil. This technique may be used either in locating larvae in soil taken from the field or in locating larvae being raised in containers of soil in the laboratory. If larvae are to be kept alive one must be sure not to over etherize the larvae, removing larvae as soon as they begin to glow under the influence of ether. 6. Large firefly larvae may be collected in the field prior to periods when adults are most active. In subtropical area like Central Florida, it may be possible to collect firefly larvae throughout the year, given the rarity of frost and sandy, loose soil. Species like Photuris and Pyractomena have larvae which are as readily collected during the fall and winter months as in the spring or summer months. I developed a fairly good method for collecting firefly Photinid larvae. This involved placing an opaque tarp or tent over the area to be searched. Then in complete darkness and after several minutes to accustom one's eyes to the darkness, one begins searching through leaf litter. When a firefly larvae is uncovered it will glow brightly for a moment. Then one can grab the specimen and place it in a collection jar. Even quite small firefly larvae may be collected in this manner. Also one may uncover Phengodes larvae, luminescent centipedes, earthworms that have luminescent organisms growing in or upon them and luminescent fungi or bacteria growing upon decaying vegetation. In fact I've had occasion to setup and live in tents in Florida, on both the University of Florida campus across form Lake Alice and at the Devil Millhopper before it was turned into a State Park. By living in the field in areas frequented by fireflies, I was able to collect firefly larvae specimens crawling on trees, observed upon leaf litter and found in decaying organic material. The following is from Firefly Notebook #6: Jan 30, 1992 - Collection of firefly larvae, Medicinal Plant Gardens, University of Florida, Gainesville, Florida. Overcast sky. Bright full moon obscured by clouds. This evening Photuris larvae were collected in the Med. Gardens. Also Photuris larvae were collected across the street from the Med. Gardens. Photuris larvae were located by observing for a glow above the ground, and by raking my hands through leaves to uncover larvae in the wooded areas. Three Pyractomena larvae were found crawling upon small twigs above the ground. Three Phengodes larvae were found in the upper layer of soil under a thick bed of pine needles. Note that all three Phengodes larvae were located in approximately the same one square foot of area. This evening the ground was moist and the temperature was mild, estimated at 65-70 degrees F. I did not hunt for Photinus larvae. 7. Once firefly larvae specimens are returned to the laboratory (or to one's kitchen table), small firefly larvae can be relocated by carefully searching through debris. Tiny larvae are very well camouflaged and look much like a piece of brown pine needle. One way to relocate them is to set collection containers in a darkened room or closet. For best results there must be no light whatsoever filtering into the room. After collection containers have been left undisturbed for about an hour, enter the room and carefully observe for the larvae to glow when one runs a soft brush through the debris. ADDENDUM: The resemblance of tiny Photinid larvae to brown pine needles which is a primary form of decaying vegetation which makes up the leaf litter in which these larvae are found may represent a form of protective resemblance. By resembling pine needles both in their shape and color Photinid larvae make it very difficult for themselves to be seen by other small predacious animals like spiders. Hence this protective resemblance may have contributed to the survival of Photinid larvae. 8. Glow may be stimulated and enhanced with a few drops of diethyl ether. This will cause a firefly larvae to glow continuously enabling one to pin point its location. Then the larvae may then be remove from a large portion of soil and debris and placed in a Petri dish with moistened filter paper or sterile potter's clay. Do not leave the larvae exposed to the diethyl ether for more than a few seconds as the larvae may expire if they are left without oxygen for too long a period. The discovery that diethyl ether would make firefly larvae glow was one I made after first observing this effect in adult fireflies. I guessed correctly that diethyl ether would have the same effect upon firefly larvae and hence make it easier to locate and collect them in the field. The only problem with this method is that one must be careful not to breath the ether fumes, especially when working in a closed or unventilated area. 9. Another useful sorting method is to wash soil debris with water as firefly larvae tend to float and can thus be collected from a handful of soil in which they were found. I've had occasion to collect upward of a dozen Photinid larvae in a few hours time using a combination of these two collection and sorting methods. In the field searching for larvae under a tent or tarp works great, especially if there are near by street lamps or light from a bright moon. Also the usage of diethyl ether to stimulate and prolong the glow of firefly larvae in the field makes it much easier to collect these elusive creatures. 10. Firefly larvae thus collected may be used in feeding trials with the objective to determine a food which may be used to rear firefly larvae. Although I have observed Photinid larvae collected in the field to eat soft bodied animals, I have not reared such larvae from egg to adult. My excuse is that I simply am not a very good nurse maid. However, I have had occasion to maintain fruit flies for dozens of generations. In fact I postulate one might be able to rear Photinid using as a food source fruit fly larvae or the soft bodies of expired adult fruit flies. I first observed Photinid to eat both adult and larvae of Drosophila in Feb. 1971. These were specimens of Photinid collected in the field near Lake Alice on the University of Florida campus. I collected these Photinid larvae by sorting through leaf litter. Then later experimented by offering them both freshly killed adult fruit flies and fruit fly larvae. I observed these large Photinid larvae apparently eating a fruit flies. I say "apparently" as the problem with observing a firefly larvae do anything is that they should be observed under darkness or very low light levels, given soil and leaf litter are a firefly larvae's natural habitat. As soon as one turns on the light or causes a vibration as by handling a Petri dish or container in which firefly larvae are maintained, this inspection disturbs the larvae. Developing a method to observe and rear Photinid without disturbing the larvae presents a challenge. The following is from Firefly Notebook #4 made in Gainesville, Florida: Feb. 5, 1971 - This evening I located seven or eight Photinid larvae in the upper layer of the soil. The ground was very moist due to rain which fell n the afternoon. All larvae were located without placing a blanket over the head. The larvae, though small, glowed brightly enough to spot despite street lights and a moon partially covered by clouds. Feb 8, 1971 - A total of ten Photinid larvae were recovered from the soil in which larvae were collected on Feb. 5, 1971. The larvae were relocated by carefully examining the soil and by floating the larvae upon water. Feb 9, 1971 - Nine Photinid larvae of 2/05/71 were fed moistened dry dog food (Purina dog chow) at 15:00 hrs. 2/08/71. The larvae were not observed to eat the food. The larvae did not collect immediately around the food as do Photuris larvae nor could I tell whether or not the larvae had eaten of the large chuck of food. I must observe Photinid larvae more closely at different hours of the day and night to see what they eat. Feb. 10, 1971 - Photinid larvae of 2/05/71 have not eaten the dog food they were given. Feb. 15, 1971 - This evening I observed Photinid larvae eat for the first time. Some adult fruit flies had been etherized, killed by mashing and placed in a baby food jar several hours earlier. Upon observing the firefly larvae at 21:45 hrs I was amazed to see them eating the fruit flies. The larvae were seen with their heads against the fruit flies apparently eating, manipulating their mandibles indicating that the larvae actually were eating. One larvae was found with its head burrowed into the thorax of a fruit fly. The larvae had gotten itself stuck inside the fruit fly and was trying to push the thorax off using its anal appendage. The larvae would stick its anal appendage to the fruit fly's thorax and push as if trying to take off a helmet. Indeed, the larvae looked like it had put upon its head a helmet and was trying to take it off! I observed the larvae at 10X and 20X to be sure that they were eating. The larvae appear to eat the inner, soft fleshy part of the fruit flies and do not eat the hard exoskeleton. I placed five freshly killed fruit flies upon a piece of moist paper towel and set these inside a jar with Photinid larvae of 2/05/71. Almost immediately a larvae had crawled upon the paper, found a fruit fly and started to devour the fruit fly by biting into the ventricle side of its soft abdomen. That Photinid larvae eat freshly killed fruit flies, Drosophila melanogaster, indicates that the larvae may eat other soft bodied cryptozoa. A survey should be made of the other cryptozoa which Photinid eat. At 20X Photinid larvae can be observed moving their mandibles together and apart in a horizontal plane chewing the food which they are ingesting. The jaw action of Photinids is similar to that of Photuris larvae. Observation of Photinid larvae manipulating their jaws is positive proof that the larvae are actually eating the fruit flies. Feb. 17, 1971 - Photinus larvae of 2/05/71 were fed five fruit flies on 2/15/71. These fruit flies were place on a piece of paper towel and twenty four hours later were gone. Eleven fruit flies were places on a second piece of paper towel and given to the Photinus larvae on 2/16/71. All but one of these fruit flies had been drug off of the paper tower when observed twenty four hours later. Apparently the Photuris larvae lift and drag off the fruit flies to eat upon them. Feb. 23, 1971 - The Photinus firefly larvae captured Feb. 18, 1971 and Feb. 5, 1971 were fed fruit flies. Fruit flies which had been etherized and frozen were placed inside baby food jars for the larvae. Several hours later I returned and watched the firefly larvae eating the fruit flies. I was one larvae eating the soft yellowish content of one fruit fly's abdomen. I watched another firefly larvae eating the insides of a fruit fly's head and bright red eye pigment was seen upon the firefly larvae's mandibles. These observations indicate that Photinus larvae eat fruit flies. The larvae appear to eat the soft body content of fruit flies without eating the exoskeleton of the fruit flies. That Photinus eats fruit flies would suggest that Photinus larvae might also eat other flies or soft bodied insects. Feb. 26, 1971 - A Photinus firefly larvae of 1/05/71 was fed large fruit fly larvae. The Photinus firefly larvae was observed eating the fruit fly larvae in the same manner that Photinus eats adult fruit flies. Feeding Photinus fruit fly larvae makes feeding behavior easy to observe as fly larvae are large and white with soft bodies that Photinus can bite into, chew and ingest. Photinus eats by biting its large mandibles into the soft body of the fruit fly larvae. Then Photinus exercises its mandibles back and forth. That Photinus will eat both fruit fly larvae and adult fruit flies must be the result of both having a similar taste to Photinus. This would indicate to me that Photinus prefers the taste of Drosophila because Drosophila larvae eats yeast. ADDENDUM: The fruit flies which I reared were the wingless or vestigial variety and were obtained from the Genetics Department at the University of Florida. These fruit flies were actually fed a crude media made from bananas and brewer's yeast. An area for future investigation would be to present a variety of soft bodied insects to Photinus in order to determine which insects or insect larvae Photinus prefers. March 12, 1971 - Eight firefly larvae of 2/05/71 were fed a freshly killed baby cockroach placing the cockroach at the edge of a moist piece of paper towel. Upon observing the cockroach 24 hours later it was found under a piece of paper towel with the content of its thorax eaten out. Although I did not observe Photinus larvae eating the cockroach, this observation suggest to me that larvae drug the cockroach under the paper towel and ate the cockroach (cockroach legs were not eaten and were left intact). This observation indicated that the diet of Photinus may extend over a wide range to include a variety of small, soft bodied animals. If one is going to rear Photinus larvae it is necessary to know what they will eat and what they won't eat that the best food for the larvae may be selected. ADDENDUM: This was most likely a German cockroach as infestations of this species in buildings in Gainesville, Florida was quite common. March 14, 1971 - A controlled experiment was conducted using two Photinus larvae collected 2/05/71. One larvae was fed a know food source, being adult fruit flies. A second Photinus larvae was fed an unknown food source, being an acorn larvae (small white grub found inside an acorn and killed by placing in warm water). The acorn grub did not appear to be eaten whereas the Photinus larvae was observed to eat upon the fruit flies. On March 19, 1971 I offered both of these larvae fruit flies. The Photinus that previously had not eaten the acorn grub was observed eating upon the fruit fly. This observation suggest that Photinus larvae may be somewhat specific in its diet, in that it may not eat all soft bodies animals. March 27, 1971 - Photinus firefly larvae collected on 2/18/71, 3/24/71, and 2/05/71 were placed in disposable Petri dishes of sterilized moist soil. The soil was plowed with a knitting needle to provide cracks and crevices in which the larvae could burrow. The larvae were provided freshly frozen fruit flies and several larvae were observed at 20X eating these fruit flies. I watched one larvae eat the eyes of a fruit fly, the larvae's mouthparts becoming brightly red. Noticing that Photinus larvae collected in nature are often colored slightly pink upon their sides, I wonder if this pink coloration might be due to the diet of the larvae, that they may have been eating fruit flies in nature? If it can be shown that the pink coloration of Photinus larvae is due to the pigment in the eyes of fruit flies, than one can deduct that Photinus larvae found in nature having pink coloration have been eating fruit flies. March 29, 1971 - Four Photinus larvae placed in disposable Petri dishes on 3/27/1971 crawled out of the Petri dished and desiccated in the bottom of a plastic container in which the Petri dishes were set. This observation indicates that Photinus larvae must be kept in tightly closed containers least they crawl out. This observation also illustrates that Photinus crawls about and squeezes through cracks and crevices which it finds. Photinus larvae may also be separated from soil by their tendency to crawl about. Also as Photinus larvae are able to burrow out of disposable Petri dishes, these larvae should be kept in tightly sealed jars, such as baby food jars, from which escape is not possible. If disposable Petri dishes are use, they should be covered with saran wrap or other plastic wrap to make a tight seal. April 2, 1971 - I had assumed that Photinus larvae kept in disposable Petri dishes of soil covered with saran wrap and a rubber band would not be able to escape these containers. However, my assumption proved wrong and came up and batted me in the face when I found that one larvae, probably a III-instar larvae, had crawled out of such a container. The larvae was found alive between sheets of moist paper towel in the bottom of the plastic freezer container in which the Petri dishes had been kept. It seems that Photinus seeks a moist place to burrow into. Thus Photinus may be kept upon moist paper towel and fed and observed regularly. Whether or not Photinus larvae need soil or leaf litter debris to to construct pupal cells is yet to be determined. If Photinus larvae need soil as to construct pupation cells than larvae should be kept upon soil or moved to soil when ready to pupate. April 5, 1971 - Of 27 Photinus larvae transferred 3/27/71 to Petri dishes, four crawled out and desiccated, one was swollen/ballooned after removing from Petri dish soil, and 18 have been recovered from Petri dishes containing soil (recovery being made by letting larvae crawl out of soil onto moist paper towel). Four larvae were missing. It is interesting to note that Photinus larvae do not die as readily when kept in baby food jars of moist soil with paper towel and fed fruit flies. I may find that the ideal culture chamber is a large hermetically sealed plastic freezer containers with an inch of moist soil and paper towel for larvae to crawl upon when moulting. ADDENDUM: Subsequently significant numbers of Photuris larvae were collected from adult females using reagent bottles with sterilized soil (See Collection of Photuris eggs in bottles ). This method worked very well and would be recommended as a routine procedure for collecting I-instar Photuris larvae. The following is from Firefly Notebook #6 made in Jacksonville, Alabama: Feb. 10, 1974 - Jacksonville, AL Photinid larvae collection and observation. At 03:00 hrs. I collected one Photinid larvae by digging in the soil of the backyard at 801 12th Avenue. The larvae was located in the upper two or three inches of soil. It glowed very brightly when uncovered. I used an army blanket over my head to shield street light and light from a bright moon. The temperature outdoors was in the lower thirties so the blanket also helped keep me warm as did the long underwear that I wore. In addition to the single Photinid larvae I found a number of earthworms which produced luminescence when uncovered. (Not sure what caused these earthworms to glow). The single larvae which I found was placed in a small Petri dish. The idea occurred to me that I might place potter's clay in the bottom of the Petri dish. As the potter's clay is moist it should act to keep the larvae from desiccating. Also, mold will not grow upon clay as it will upon moist paper towel. Clay is in essence very similar to the natural soil medium in which the larvae lives, the primary difference being that clay is of a very firm, non-porous, relatively sterile consistency, where as the larvae's natural medium is course, porous soil teaming with animal life. If the larvae will survive in a Petri dish of moist clay, this may prove an ideal medium for use in rearing Photinid larvae as well as other firefly larvae (Photuris and Pyractomena, etc.). Clay may be used as a medium upon which to collect firefly eggs, as a medium for rearing I-instar larvae, and as a medium for older larvae and in which to allow larvae to pupate. A firm layer of clay can be broken up with a needle to make groves in which adult fireflies rearing may lay their eggs and to provide course clumps of clay that larvae may manipulate to build pupation igloos. Also firefly eggs can be readily washed from clay. A large number of P. pyralis fireflies kept in a terrarium may deposit eggs in clay and then the eggs or emerging larvae easily collected by washing the clay into suspension and through a fine screen which will catch the eggs or larvae. After placed in the Petri dish the first thing that the Photinid larvae did was to clean its body with its anal appendage, which it did by wiping the appendage over each segment beginning at the anterior end and working to the posterior end. After washing its left side the larvae washed its right side. I place a small aquatic snail to the larvae. As I watch the larvae is walking about inside the Petri dish upon the surface of the clay perhaps in search of a crevice or hole to burrow into, or perhaps seeking to escape the light. Can the larvae dig a hole in the firm clay? Can the larvae build an igloo out of the firm clay? (Note that the larvae was motionless after I first brought it inside form the cold. Perhaps the larvae was motionless due to the low temperature and/or handling. The Photinid larvae collected Feb. 10, 1974 is still alive. It has been kept in a small Petri dish with potters clay and a small earthworm (See Observations of Photinid larvae in rearing chamber and Rearing chamber for Photinid larvae ). When observed the earthworm was coiled up into a ball. I stuck the earthworm with a pin and it moved to indicate that the earthworm was still alive. The Photinid larvae had moulted once. There is slight mold growth upon the clay in the Petri dish. The mold is obviously growing upon moisture condensed upon the clay and perhaps upon earthworm slim or excrement. The Photinid larvae does not appear to have eaten of the earthworm. March 23, 1974 - The Photinid larvae collected Feb. 10, 1974 has completely devoured the earthworm which was placed with the larvae inside the Petri dish. The larvae was observed to have moulted previously but today no sign of its moult skin is seen. Did the larvae also eat its own moult skin? Also the larvae has been digging in the clay soil as evidenced by many small round balls and globs of soil apparently the result of the larvae's digging efforts. Does this digging indicate that the larvae may be ready to pupate and construct an igloo? The larvae should be fed a second earthworm and given some dry powdered clay with which it can construct an igloo. Note that I have been keeping the larvae's Petri dish sat inside a covered shoe box set that is placed upon a northern exposed window ledge (indoors). Can the larvae detect daily changes in length of daylight from within the shoe box? I would speculate that if the larvae is able to detect small changes in the period of light and dark that this sensory ability is greatly hampered by the reduced light intensity fluctuation inside the box. Also as light exposure in of greatly reduced intensity, the larvae probably does not exhibit sharp behavior change as it would had the larvae been exposed to natural changes in daylight intensity and length. April 7, 1974 01:30 hrs. Photinid larvae of 2/10/74 was observed to be still alive. However the clay in the Petri dish was drying out and the larvae appeared thin, as though it had lost water through evaporation (desiccation). The larvae was removed from the Petri dish, washed in water and replaced in the Petri dish after adding some fresh moist clay. A small section of clay was place atop the layer of clay in the Petri dish that the larvae might have a dark place to crawl beneath. The Petri dish was set inside a 16 oz. coffee can which had a layer of moist clay in the bottom of it, and the whole was covered with a plastic lid. This arrangement should preserve a high humidity level inside the Petri dish for a number of months. Also as light can enter into the enclosure and stimulate the larvae, the larvae can respond to normal daylight periods which may effect pupation. For this reason the coffee can is sat in a window (North exposure) that indirect sunlight may be visible to the larvae. April 16, 1974 - Photinid larvae of 2/10/74 was observed to be still alive in the above described Petri dish/coffee can container. The larvae needs to be fed an earthworm or it may die. Hence an earthworm was fed to the larvae at 01:25 hrs. April 16, 1974. Will larvae eat the earthworm? If larvae had a variety of different soft bodied foods to choose from, which would it eat: snail, earthworm, fly, fly larvae, slug, etc. ? April 16, 1974 23:10 hrs. - Photinid larvae of 2/10/74 was observed this evening. The larvae has begun to eat the earthworm that it was given 22 hours ago. The larvae was observed under the piece of clay and the earthworm was seen to be cut into three pieces. The larvae has swollen up as though it had filled with fluid from eating the earthworm. Might larvae be stimulated to pupate after eating large numbers of earthworms available in the Spring? It should be noted that the three sections of earthworm were about one centimeter apart indicating that the larvae may have pulled or dragged the earthworm after killing it, or may have devoured center sections of the earthworm. April 17, 1974 - Photinid larvae was observed at 16:l5 hrs to have eaten the above three pieces of earthworm and to be in the process of eating the last remains of the earthworm. The larvae had a small piece of muscular flesh in its mouth parts and was apparently just completing its meal. The larvae has swollen up into a very bulbous creature. The larvae does not appear to have eaten the "feces" or non-digestible stomach content of the earthworm. Note that mold mycelium can be seen beginning to grow on undigested remains of the earthworm. When disturbed in its feeding the larvae stopped feeding and began to crawl around. The larvae is probably sensitive to handling (tactile stimulus) and to high intensity light used to make observations. At 17:00 hours the Photinid larvae was given another 3-4" long earthworm. April 18, 1974 03:20 hrs. Photinid larvae has begun to eat the earthworm it was given at 17:00 hrs on Aug. 17. The earthworm has been divided into three segments and the larvae appears to be eating upon the center section. Both the anterior and posterior sections of the earthworm were observed to be moving, wiggling slightly back and forth; however, these segment have lost control over their mobility. It is an interesting fact that the larvae began to eat a second earthworm after it just completed eating a first earthworm. ADDENDUM: Twice the Photinid larvae was observed to divide an earthworm into three section. This behavior seems designed to permit the extremes of the earthworm to remain alive until the center section is devoured. Then the larvae eats the other two sections. This is a very interesting eating behavior for rather than eat an earthworm one end to another, the larvae attacks the earthworm and chews it into three pieces, eats the midsection, then eats the remaining two end sections. Does a Photinid larvae always eat live earthworms in this manner? How many earthworms will a larvae eat in its live time (obviously this depends upon the size of the earthworms. Probably larvae eat as many or as much in earthworm flesh as required for their complete growth and development, as is generally the case with a living organism. April 29, 1974 00:15hrs - Photinid larvae is still alive. The earthworm also is still alive and seems to have healed from the larvae's having eaten the part of the posterior half. The earthworm had found its way between the lid and the Petri dish and crawled out of the Petri dish into the coffee can. I replaced the earthworm into the Petri dish with the larvae. The Photinid larva was rinsed off in water as some clay was sticking to its body. Will the larvae eat the rest of the earthworm? When will the larvae pupate? The larvae will most probably pupate in June if provided abundant food. May 5, 1974 - Photinid larvae had crawled out of Petri dish as did earthworm. Both were alive inside coffee can. That larvae can crawl out of a covered Petri dish indicates the need to keep it in a baby food jar or to keep Petri dishes inside a coffee can with plastic lid (or wrap Petri dishes in saran wrap). Larvae was replaced into Petri dish and provided a snail that was found outside under a stone. May 11, 1974 - Photinid larvae did not eat snail after 24 hrs so was given earthworm which it has not eaten yet. ADDENDUM - The above observations confirm that Photinid eat earthworms. I highly suspect that the Photinid of 2/10/74 was a P. pyralis larvae but I can not be certain of this as I did not have the species of the emerging adult determined. However these observations highly suggest that Photinid, and probably P. pyralis may be reared by feeding them earthworms. Given I have also observed Photinid eat fruit flies and cockroaches, it is likely a technique which employs these or other soft bodied animals would be successful rearing. 11. The above observations suggest that to rear Photinid fireflies they may be fed the soft bodies of freshly killed insects. Since flies, fly larvae and cockroaches inhabit the same region where these firefly larvae naturally occur it is very reasonable and quite probably Photinid can be reared upon the soft bodies of these animals. I would also suggest that Photinids may eat the soft bodies of any insects they find while scavenging the cryptosphere, burrowing or crawling through soil or leaf litter. In fact I would suggest that the fact P. pyralis and other Photinid larvae do not have a tooth upon their mandibles relates to the fact these larvae tend to eat the soft body tissue of living animals such as earthworms, rather than dead insects and insect larvae (although these will be eaten in captivity or in nature should they be offered or encountered). A tooth has not developed upon the mandible of Photinid larvae as it has with Photuris larvae as it is not necessary when eating the very soft bodies of living earthworms, snails, insect larvae or tiny dead fruit flies which are digested by liquefying the flesh of living animals and then drinking it. This does not preclude the fact firefly larvae have also been observed to eat dead snails, earthworms, fruit flies or other soft bodied animals in the laboratory. In other words, the fact that Photinid does not have a tooth on its mandible is a strong indication that its preferred natural food is living soft bodied animals, which it preys upon and kills by eating it alive, earthworms being a primary prey of Photinid. 12. The larvae of Photuris and Pyractomena are somewhat easier than Photinids to rear. Observation I made in June 1970 showed that I-instar Photuris larvae hatched from eggs will eat boiled snail. I learned from Dr. James E. Lloyd in early 1971 that Photuris larvae collected in the field will eat an artificial diet of moistened dried dog food. Pyractomena eat snails. When I collected Photuris eggs from adults and reared them to I-instar larvae at the University of Florida in 1971, the larvae were observed to eat dried Purina dog food which had been moistened. This would suggest that Photuris larvae may be reared upon moist dog food or some other artificial media, such as a mush of earthworms or snails, which would probably better resemble their natural food. The primary problem here is that moist fleshy food quickly rots or becomes moldy and bacteria and mold may frustrate efforts to rear fireflies. Possibly employing a mold inhibitor as is used in fruit fly culture media, would solve this problem. Figure 4. I-instar Photuris larvae at 50X Note body is broad and flat as compared to that of a I-instar P. pyralis larvae which is long and narrow. This is characteristic of a larvae which has a roving, scavenging behavior which searches through leaf litter atop soil for its food. Also (not shown here) Photuris larvae have a tuff of hairs around their mouth parts which serve as a sort of filter. As will become apparent, these anatomical differences between P. pyralis and Photuris have evolutionary significance directly related to the different feeding behavior of each larvae. This photo also shows nematodes inside the larvae. The following is from Firefly Notebook #3 made in Jacksonville, Alabama: June 24, 1970 22:05 hrs.- Photuris larvae. One larvae of Photuris was observed to have hatched out of an egg laid June 10, 1970. Hence incubation period was two week. The larvae is about 2.5mm in length and was seen walking around. The larvae walks at a very fast pace. The larvae was picked up in a drop of water and placed on a sterilized piece of paper towel in a separate Petri dish. The larvae responded by rolling itself up into a ball. ADDENDUM: This behavior or rolling up into a ball is much like that of sow bugs. When the young I-instar Photuris larvae roll into a ball it protects its head and soft belly and leaves only its upper armored surface exposed. This defensive behavior, coupled with the fact Photuris larvae also blink brightly when uncovered in the field, suggest that the combination of rolling into a ball and flashing brightly serves to warn off enemies? Could the "enemies" be other firefly larvae which are cannibalistic, especially when they first hatch out of eggs? If this behavior identifies firefly to each other and prevents cannibalism, then it would be advantageous for the survival of the species. Obviously if two young Photuris larvae meet and both respond in this manner they would both protect themselves from being attacked by the other. Or does this defensive behavior protect Photuris larvae from predaceous by other animals like spiders? June 24, 1970 (continued) - A small snail, about 7mm in diameter, was offered to the I-instar Photuris larvae. The larvae crawled upon the snail's shell and onto the snails slimy portions at the opening of the shell, the snail being inside its shell. Here the larvae slowly crept into the slime and/or rather swam, as if eating slime. Is the larvae really eating the snail's slime? Will the snail come out of its shell and try to escape from the larvae or eat the larvae? Is the larvae stuck in the snail's slime unable to escape? The larvae was observed at 20X with a microscope and seen to be exercising its mandibles and pulling its head in and out. The snail began to come out of its shell but for some reason as if suddenly stung, quickly went back into its shell, perhaps being disturbed by my making vibrations or the larvae biting the snail. Again the snail tried to come out of its shell but quickly retracted. I don't think it was I which disturbed the snail. Is a larvae able to attack itself to a snail and act as a parasite, the larvae just having emerged from its egg? Is the larvae able to bite the snail and cause the snail to retract into its shell? The snail was observed to come out of its shell and crawl away leaving the larvae apparently stuck in slime. I am not certain whether the larvae is stuck in slime or just clinging to the slime, holding on to the slime as though it were a prized feast meal. ADDENDUM: The fondness Photuris larvae show for snails may suggest Photuris is a snail predator. It would be informative to offer various soft bodied animals to both Photuris and Photinid larvae to help establish what soft bodied animals firefly larvae eat, to observe and record predation, and to access whether gradation or scavenging for dead insects is how firefly larvae eat in nature. As Photuris eggs from which the larvae hatched were exposed to 12 hours of daylight (kept under a 20 watt mercury vapor lamp) and handled by the method of placing eggs in water, neither light nor water seems to effect the larvae hatching from eggs. In several eggs which have yet to hatch, developing larvae can be seen with magnification of 20X. The larvae are rolled up inside the eggs, their red mandibles, black eyes and segmented bodies all visible through the thin yellow-green egg shell. On eggs which molded can be seen there are no fully developed larvae visible inside the eggs. June 25, 1970 17:20 hrs. - Three more Photuris larvae of June 10, 1970 have emerged from their eggs. The larvae have changed from a white color to a black or gray color. The larvae were placed in Petri dishes with the larvae hatched on June 24, 1970. June 26, 1970 02:00 hrs. - Two more Photuris larvae were found from eggs of June 10, 1970. This brings the total number of larvae hatched from eggs to six. What do these larvae eat? Try feeding aphids. Capture cryptozoa with Berlese funnel and feed to larvae. Three more larvae were observed, one having just emerged from its egg and colored with black eyes, reddish mouthparts, yellowish organs down mid back region and colorless lateral body parts. The second larvae observed was scrambling head first out of its egg. June 26, 1970 (later same day) - Photuris larvae. Six more larvae were added to a baby food jar in which larvae are being kept. The total number of larvae hatched is now 12. One additional larvae is in the process of hatching from its egg. Larvae walk around at a rather rapid pace. When disturbed or handled, larvae roll into a ball. Inside baby food jar larvae can be seen crawling about on the moist paper towel. Are larvae looking for food or a dark soil retreat? A larvae was placed upon moist white sand where it preceded to walk around, not dig or burrow, perhaps because the sand is too wet, or perhaps because digging and burrowing is not the habit of Photuris larvae. The larvae was offered a piece of boiled snail meat which the larvae crawled upon and then off. The larvae was offered a small live snail which the larvae crawled upon, but as the snail slipped away the larvae was left behind in the slime. The larvae remained in the slime for a minute and then crawled on. The larvae was offered a sow bug but instead of eating the sow bug, the larvae just crawled upon the sow bug and took a short ride. This is probably not a natural behavior of Photuris larvae. It may be that larvae eat only in darkness. The larvae was offered a dead sow bug and as soon as the larvae crawled upon the sow bug, the Petri dish was covered with a tin can. Returning after five minutes I found the larvae still upon the sow bug. This indicates larvae may eat meaty material provided the larvae are kept in the dark. Larvae probably seek shelter when exposed to light. To determine what food larvae like to eat place several types of meaty food upon paper towel with larvae and sat in a dark room. Return after an hour or more and observe which food larvae are found upon. Do larvae tend to collect around any particular food after about 12 hours? ADDENDUM: Subsequent observations of Photuris larvae collected in the field indicated that they do seem to have a roving, predacious or scavenging behavior. They may also readily attach themselves to debris or other soft bodied animals. So it is quite possible firefly larvae may chance to attach themselves to a snail or other soft bodied animal upon which they could feed. June 27, 1970 - Feeding Behavior of Photuris larvae - I-instar larvae were offered boiled snail on June 26. At 22:30 hrs. June 27, larvae and food were observed, having been kept under a tin can (in the dark) since food was added. The food appeared partially devoured and around several of the pieces of food could be seen smaller clumps of debris. Apparently the larvae feed upon the boiled snail meat leaving behind a mess of scattered food. The larvae had also been offered honey upon a piece of paper but I was not able to tell whether the larvae had eaten the honey. A single larvae which had been placed in a Petri dish of white sand was observed and found apparently not to have eaten the dead sow bug which was offered the larvae. The larvae had not burrowed under the sand indicating that Photuris larvae do not burrow. That Photuris larvae do not burrow falls in line with the observation that these larvae are well equipped with legs, an anal appendage and toothed mandible which they can use to crawl and prey upon small soft bodies animals. Larvae probably spend their time in the upper layer of loose organic decaying material of the cryptosphere. Among decaying leaves, pine needles, rotting wood and loose soil the larvae probably crawl in search of food. ADDENDUM: This observation as to the habitat of Photuris larvae was later confirmed when I went to Gainesville, Florida and spent considerable time in the field hunting through leaf litter for firefly larvae. Photuris larvae are relatively easy to find in the Central Florida woodlands as the crawl about through leaf litter, apparently looking for food. June 30, 1970 02:20 hrs. - Photuris larvae food. Photuris larvae were observed to have eaten two whole small pieces of boiled snail offered on the 29 of June. The larvae have begun eating a third piece of snail. Two larvae were observed around a piece of snail when the tin can covering the baby food jar was first removed. One piece of snail was covered with mold hyphae and sporangospores and was remove. The larvae were place in a clean jar with fresh moist paper towel and boiled snail. Only ten larvae of twelve larvae in this container were present. Either two larvae escaped through the loose top, which from now on will be secured, or other larvae ate the two missing larvae, probably having become strong by eating snail meat. To date I have collected 13 Photuris larvae but only have 11. A 14th larvae was added today bringing the total number of larvae to 12. After only a few minutes in dark larvae which had been placed in a fresh container and given fresh boiled snail were observed. These larvae were collected on one piece of snail and one larvae was crawling on a second piece of snail. That larvae collect upon boiled snail meat implies that larvae eat boiled snail. If larvae eat snail and similar meat all there lives, then rearing larvae to maturity should be no difficult matter. One need only provide larvae with a moist, clean environment and feed them like they were babies, as indeed they are, glowing, growing baby fireflies. July 1, 1970 - Photuris larvae appear to have been eating boiled snail, small bits of debris appearing around the clumps of food. A small snail was killed by cracking its shell, spearing crudely with a needle and ripping apart its gray flesh, tearing out the flesh from the shell and offering this to Photuris larvae. About ten minutes after being offered fresh snail meat, three larvae can be seen collected around the meat apparently eating. Though the larvae were kept in the dark about ten minutes after giving them the snail meat, the larvae do not retire from the snail, now being observed in dim light. July 2, 1970 - Photuris larvae were observed at 02:10 hrs. Two larvae were near snail meat given the day before. One larvae hers stuck in the snail meat was washed off and replaced. Larvae appear increased in length since having emerged from eggs. A larvae was picked up with a paint brush and placed upon a centimeter ruler. The larvae measures about 3 mm. A black slimy substance was observed upon the larvae's mouthparts. This substance is probably the black slimy meat of the snail partially digested by (the powerful saliva of) the larvae. That the larvae has this black slimy substance, partially digested snail meat, upon its mouthparts is a strong indication that the larva has been eating the freshly killed snail. July 3, 1970 - Photuris larvae cannibalism - One Photuris larvae was accidently mishandled when removing food. To try to amend my carelessness I washed the larvae off in a cup of water, picked it up in an eye dropper and placed it back in its container with other Photuris larvae. The larvae did not move around, seeming dead. Five minutes later I came to check up on the larvae and found that had been taken care of by its comrades. A fellow larvae had found its comrade and was observed with its mouthparts in the dying larvae's back. The cannibalistic larvae had crawled upon its comrades's back apparently sticking its fangs into the damaged larvae. The eating larvae held itself in place by securing its foot to the paper towel, hunching its body and head up over its victim so that legs and mouthparts were on the victims back. Though larvae are cannibalistic this behavior may be a ritual reserved for dead or disabled comrades. ADDENDUM: Subsequent observations of Photuris larvae indeed showed that they were quite aggressive and will not hesitate to eat the flesh of other dead, disabled or dying larvae of their own kind. Photuris larvae also seem to act like little carnivorous wolves, gathering around food to eat and being disturbed or annoyed if another larvae gets too close. The following is from Firefly Notebook #4 made in Gainesville, Florida: Feb. 4, 1971 - Twenty Photuris larvae collected 1/15/71 have been kept without feeding in a large cylindrical glass bowl covered with a glass plate. Today the larvae were given dry dog food which had been moistened with water. The larvae were observed collected around the food eating. The larvae would tear off a chuck of food and chew it with their mandibles. Two larvae were observed to have a fight, one larvae biting the other and chasing it away. I observed seven larvae eating dog food. That larvae eat dog food indicates to me that they may also eat organic decaying material found in the cryptosphere. Feb. 8, 1971 - Photuris larvae of 1/15/71 were fed dried dog food placed upon a piece of paper towel. Minutes later four larvae were seen collected around the food eating. The larvae drug the food one inch off the paper towel, a testament to their ravaging strength! Feb. 9, 1971 - The Photuris larvae of 1/15/71 ate all the dried dog fed to them 2/08/71. Of this dog food there remains only a small bite of scattered food. Several of the Photuris larvae have constructed cells or igloos underneath the soil. As I have never seen Photuris construct an igloo, igloo construction would be interesting to observe. It would also be interesting to observe the moulting of Photuris larvae. Feb. 10, 1971 - The dog food fed Photinus of 1/15/71 was devoured and only crumbs remained spread about upon the paper towel on which food was offered. Mold had begun to occur on the dog food so it was removed. Feb. 17, 1971 - Photuris of 1/15/71 can be seen to have burrowed under the soil to form igloos, pupation chambers, or cells. The Photuris larvae burrows about an inch beneath the soil where they construct chambers. Feb. 23, 1971 - A living snail was places in a baby food jar with a Photuris larvae. The larvae apparently ate the snail as the snail shell was empty several days later. A snail of a different variety was fed to this same Photuris larvae. Upon inspection this snail was partially devoured as indicated by only a portion of its body content visible when the shell was held up to a bright light. Conclusions: Form these observation I developed a method for rearing Photinid fireflies. Basically this consists of collecting adult Photinid (namely P. pyralis) fireflies, letting the adults mate in a terrarium, allowing the females to deposit their eggs in soil, then collecting the eggs in a dish of water. The eggs can be incubated at room temperature for 14-16 days until larvae hatch. Then the young larvae are fed and reared upon the soft bodies of freshly killed insects, using fruit flies as a primary food, given fruit flies are very easy to rear and maintain in the laboratory. Were one to have a source of earthworms this would make an ideal food for P. pyralis larvae, especially as they mature, and is the food I recommended for rearing P. pyralis or other Photinid to the pupation stage. For rearing I-instar Photinid, glass Petri dishes may be used as may any small jar or container such as a baby food jar. The type of container is not so important so long as it has a tight seal. Also it is important to maintain sterile conditions and not allow too much moisture to condense upon the side of containers, as I-instar larvae may become trapped in the surface tension of a water drop and expire. For this reason I suggest using a layer of moist and sterile potter's clay in Petri dishes or small jars in which larvae are reared. Also moist filter paper may be used for this purpose. The biggest problem is allowing food to rot due to bacteria or mold before larvae can eat it. Hence larvae should be fed only very small amount of food at a time. One should add food and remove any uneaten food within 24-48 hours, replacing it with fresh food. In this manner problems with mold and bacteria contamination may be reduced. One may also want to try using mold inhibitors, as is done with fruit flies, to limit the occurrence of contamination, especially in mass rearing attempts. Photinid larvae have obviously solved the food rotting problem by evolving to eat their prey alive! Hence in rearing these larvae in the laboratory I recommend feeding them living earthworms. As my observations have shown, Photinid larvae are able to prey upon earthworms and has an established behavior for eating earthworms alive such that this food source does not decay before even large earthworms can be eaten by smaller larvae. For mass rearing I propose using a freezer container with a tightly fitting lid. Stack sterilize paper towels loosely to provide cracks and crevices for larvae to explore. Feed firefly larvae freshly killed or frozen fruit flies placed between the paper towel layers. If mold is a problem paper can be dipped in Tegosept-P, a mold deterrent used in fruit fly culture. Remember that a degree of moisture is sufficient to prevent the larvae from drying out, which is also prevented by regular feeding. Keeping larvae in small Petri dishes or jars with a moist substrate seems to work well and this is what I would recommend to anyone attempting to mass rear Photinid. An alternative is to use large rearing trays with soil that contains earthworms. Simply allow adult female to deposit their eggs in soil which contains earthworms. The Photinids will then be provided with their natural, preferred food source (See Mass rearing cages for Photinid larvae ). As of this writing I have not attempted to mass rear Photinids from egg to adult. But the basic techniques and methods herein established through my accumulative observations and experiments may help others to rear fireflies from egg to adult in sufficient numbers to make genetic and other studies. With respect to the feeding behavior of Photuris larvae vs. Photinid larvae, Photuris larvae appears to have a roving, scavenging feeding behavior, to search through the upper layers of leaf litter and soil debris, to be opportunistic and to eat any type of suitable soft bodies animals, alive or dead which it may chance to encounter. In contrast Photinid larvae are far more host specific and tend to have a burrowing behavior in keeping with the fact their preferred food is earthworms which they prey upon and eat alive. With regard to what is the significance of the fact that Photinid has a grooved mandible which does not have a tooth and Photuris has a grooved mandible which doe have a tooth, the difference or contrast in their feeding behavior suggest an evolutionary explanation for this anatomical variation in species. Initial observation of Photinid eating upon freshly killed and live earthworms may suggest Photinid always naturally eats upon living animals which it injects with a potent saliva to immobilize and digest its prey. Photuris on the other hand may more readily scavenger for its food, eating the dead bodies of small animals, such that much of its food source is of a harder nature and is actually torn apart and chewed (as in the case of eating dog food in the laboratory). Hence Photuris larvae has evolved a tooth on its mandibles in keeping with or concurrent with its behavior of chewing, ripping, tearing apart and generally masticating the carcasses of dead, small bodied animals. Photuris larvae would, in theory, even eat the tissue of decaying birds or mammals (which is not too far fetched an idea when one considers dried dog food contains beef and chicken). In contrast, Photinid larvae does not normally eat dead animals, but prefers a diet of living soft bodied animals like earthworms which it literally eats alive. Hence Photinid larvae have not evolved to have a tooth upon their mandibles. The mandibular tooth of Photuris larvae may also indicate that it scavengers for and eats a larger variety of food than does Photinid larvae, such that Photuris larvae may naturally eat a wide variety of soft bodied animals which it finds dead and decaying, such food being more coarse in nature than, say, an earthworm. This could explain why Photuris larvae will eat dried dog food which has been moisten while Photinid only eats soft bodied animals like earthworms which it liquifies and eats alive! The significance of this observation is that it shows an example of how behavior in insect larvae relates to the variation in anatomy of species. The difference in the behavior of Photuris larvae and Photinid larvae has resulted in the fact Photuris larvae has a toothed mandible while the other (Photinid larvae) lacks such a tooth. This is clear evidence of how a slight variation in behavior lends itself to variation in species. Questions for further study or research: There is a need for others to repeat and follow up on these studies so as to gain a more comprehensive understanding of firefly larvae and their behavior over a wide range of genus and species. Hence these questions are posed hoping they will stimulate interest, provide others with a challenge for intriguing research and help glean a better understanding of firefly larvae behavior. 1. Given that Photuris larvae appears to be a scavenger of soft bodied animals, what variety of soft bodies animals will various species of Photuris also pray upon? Generally I've observed Photuris eat dead food which it was offered. In contrast Photinid larvae eat living earthworms. Although Photuris may scavenger for dead food, it would also be informative to make observations of Photuris eating live animals and to determine a range of living and dead soft bodies animals Photuris will eat, endeavoring to document feeding behavior with photography or video. Offer Photuris such as live soft bodies animals as insect larvae, earthworms, snails or other soft bodied animals and record the resulting feeding behavior, if any. To increase change of being able to observe and video feeding behavior, may first starve larvae a few day or a week before offering it live food. 2. What other small animals, besides fruit flies and cockroaches, collected with a Berlese funnel and occurring naturally in the cryptosphere where firefly larvae are found will Photinid larvae eat (dear or alive)? What additional live, small bodied animals, if any, will Photuris capture and eat? 3. Make a video of firefly larvae building a pupation cell. Make models of both Photinid and Photuris to use in illustration of their different body forms and how these relate to their behavior. Such models could also be used to create 3D computer graphics and animation of firefly larvae feeding behavior (in the same way movie studios have done with dinosaurs). Computer animation of firefly larvae would both educational and informative and may be used to bring the behavior of these interesting creature to the attention of a wider audience, so as to stimulate an interest in firefly studies among young people, students and naturalists. 4. Is there any relation to diet and pigmentation of Photinid larvae, as in the case of Photinid observed eating the red pigment from fruit fly eyes? 5. What different varieties of snails and earthworms with Photuris eat? Having observed Photinid eat living earthworms it would be interesting to observe this behavior for both Photinid and Photuris, endeavoring to video the behavior. 6. Can Photinid larvae kill fruit fly larvae before eating them or does Photinid larvae only eat dead animals? Also make additional observations to see if Photuris can capture and kill various forms of fly larvae. 7. How many moults does a P. pyralis larvae go through before pupating? How long does this take? 8. Collect Photuris larvae and video tape their eating behavior, igloo building behavior, metamorphosis of the pupae into adult fireflies and emergence from pupae. 9. How do Photinid larvae use their anal appendage? Several observations indicate that firefly larvae use their anal appendages in a variety of ways. First they appear to be used to provide a secure and firm hold as when walking up vertical surfaces or when pupating. Larvae have also been observed to fasten themselves to snails, sow bugs, fruit flies and other soft bodies animals presented to them. Also larvae were observed to use their anal appendage for leverage, as while holding onto a fruit fly, then burrowing into the fruit fly and pulling their bodies in and out of the fruit fly while eating. This suggests firefly larvae may aggressively attach themselves to soft bodied animals and they virtually eat them alive! In fact that is the very behavior Jean Henry Fabre observed when he described firefly larvae eating snails. In addition firefly larvae use their anal appendage to clean themselves. 10. What is the chemical nature of the digestive enzyme used by firefly larvae? This enzyme must be very strong as it is injected into the flesh of small animals to then dissolve tissue which is ingested by the firefly larvae. Establishing the chemical nature of this enzyme and synthesizing it may lead to applications in food processing and preparation or even medical uses. 11. Will one obtain better results trying to rear firefly larvae in a sterile environment or in a terrarium which duplicates the natural conditions? This question comes into play given that while trying to rear firefly larvae I have observed predacious mites, nematodes, mold and bacteria, especially when examining larvae and/or adults which have expired. In some cases these may be indicative of decay organism which naturally begin to multiply when a firefly expires. Yet when mites have been observed upon firefly larvae there is obviously an incidence of predacious mites. Given the natural food of firefly larvae is living and not sterile, such as earthworms and snails, these introduce contamination into the rearing environment. Yet healthy firefly larvae may be able to resist infestation. Generally I have tried to reduce the occurrence of predacious parasites by sterilizing soil or substrate used to collect firefly eggs and larvae. However it may be that one may obtain best yields and results by rearing firefly larvae in terrarium environments which tend to reproduce the natural environment of firefly larvae. Other Lynch Sites Project K9 | Blinks and Links | Bioluminescence in Fireflies: The luciferase-luciferin reaction in Photinus pyralis | Part I: Application of Torque to Induce Simultaneous Flight Response and Synchrony in Drosophila | The Amateur Naturalist | Firefly Notebooks | Contact the author Copyright 2000 by Terry Lynch. All Rights Reserved. This original document was compiled 1-3 Dec. 2000 from Firefly Notebooks which the author, Terrence A. Lynch, has maintained.

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