Fireflies are a joy to watch on a warm summer's eve. The adults fly about and flash looking for a mate. Once a female is fertilized she deposited her eggs in the soil and then they hatch in about 14 to 18 days. I learned how to rear fireflies while living in Jacksonville, Alabama, where Photinus pyralis was very abundant. Later I applied the same methods to Photuris sp. If one takes the proper care it is easy to rear fireflies. There are a few tricks I've learned in this regard over the years and I would like to share them with others who may enjoy cuddling up with living lights and watching them grow and glow.

For the sake of entertainment and education what I'm going to do is record the rearing of Photuris fireflies over a period of time. Observations will be supplemented with photographs and video to document the process from start to finish. In this way you may best learn and be able to collect and rear your own fireflies.

Let me begin with the collection of firefly eggs. On July 14, 2010, a single adult Photuris female was collected in Chevy Chase, Maryland, by an associate, Hess Muse. Ms. Hess had become very interested in fireflies after joining the Boston Museum of Science Firefly Watch. When she later discovered I had been rearing fireflies for some years, she wrote to me for information. Following directions which I sent to her, she collected some firefly eggs and posted them to me via overnight mail Express mail (which, of course, did not arrive over night, but after 48 hours). We were worried that the eggs might be killed if they got too hot during shipping. Hence, the eggs had been carefully packaged in a glass vial with moist soil, wrapped with bubble wrap and aluminum foil, and posted in an Express Mail envelope. This insulation helped protect the eggs from over heating during shipment.

Fig. 1. Egg of Photuris sp. showing distinctive "--V--" ridges and abdominal segments. Photo © 2010 by Terry Lynch.

When the "Yankee" firefly eggs arrived I photographed one by placing it in water on a concave microscope slide. See Fig. 1. It was easy to see the developing larvae inside the egg was a Photuris larva given the angular "--V--" ridges of its abdominal segments. I placed the firefly eggs upon a moist piece of cotton swab inside a Petri dish; this was set inside a larger plastic container with a tight fitting lid to which a piece of moist paper towel was added. See Fig. 2. The biggest danger for firefly larvae is desiccation, or drying out. Using a double container system maintains a high humidity and helps prevent drying out. Also firefly larvae can crawl out of a container so by using two containers, the outer container with a tight fitting lid, larvae cannot easily escape.

Fig. 2. Petri dish with moist cotton pad upon which firefly eggs in soil debris have been placed for hatching. The Petri dish is set inside a second larger plastic container. Photo © 2010 by Terry Lynch.

I set the Petri dish of firefly eggs on a counter where they could remain undisturbed. Then during the middle of the night I carefully took the Petri dish of firefly eggs into my bedroom and cuddled up with them under a thick quilt. After allowing my eyes to adjust to complete darkness for a few minuted I lightly tapped upon the Petri dish. Suddenly the firefly eggs glowed brightly in alarm to the vibrations! This bright green alarm flash indicated that the firefly larvae were alive inside the eggs, had survived their shipment across country, and would soon hatch.

Indeed, the first few firefly larvae hatched after 17 days of incubation. I placed the Petri dish with fireflies upon the stage of a microscope and took a few photographs of the newly hatched firefly larva. See Fig. 3. I also made a short video of one of the newly hatched Photuris larva.

Fig. 3. Photuris firefly larva shortly after hatching from egg during the early morning hours of 1 August, 2010. Photo © 2010 by Terry Lynch.

It is amazing how the firefly larva is rolled up and fits inside a tiny egg. In Fig. 4 you can see one of the Photuris larva next to an egg.

Fig. 4. A newly hatched Photuris firefly larva (Top) appears quite large in comparison to the greenish firefly egg (Bottom). Photo © 2010 by Terry Lynch.

In Fig. 5 a Photuris larva is shown right after it hatched from its egg with its anal appendage still clinging to the withered egg casing.

Fig. 5. Photuris larva has just hatched from its egg, expanded many times in size, and is seen here with its anal appendage still clinging to its withered and crumpled egg case. Photo © 2010 by Terry Lynch.

In Fig. 6 a pale Photuris larva uncurling as its body slowly fills with air expanding in size from the small spherical ball which was its egg is shown right after it hatched from its egg with its anal appendage still clinging to the withered egg casing.

Fig. 6. A creamy white Photuris larva as it emerges from its egg. The larva was manipulated with a small red sable artist's brush for this photograph. The larva was still in its egg six hours earlier and at this moment is slowly increasing in size, pumping its body with air, gradually uncurling in the process of opening up. Here only one leg has uncurled and the larva continues to fill with air. Photo © 2010 by Terry Lynch.

In Fig. 7 a tanned Photuris larva is shown upon cotton swab some 48 hours after first eggs hatched.

Fig. 7. Photuris larva has tanned and is shown upon cotton swab some 48 hours after the first eggs hatched. Photo © 2010 by Terry Lynch.

In Fig. 8 Photuris larvae have been transferred to a Petri dish of compacted moist red clay soil which was previously sterilized in the oven, let cool to room temperature, and then approximately 8 ml of purified water were added to the soil. A glass cover slip has been set upon the soil to provide a secure place where Photuris larvae may retreat. A piece of live earthworm was set upon the soil and later Photuris larvae were observed feeding upon the earthworm which became motionless after Photuris larvae injected it with venom and fed upon the earthworm as it is turned to liquid.

Fig. 8. Photuris larvae inside Petri dish upon compacted red clay soil. L1 shows Photuris larva feeding upon a small piece of earthworm which is becoming liquified as the Photuris larva feeds. L2, L3 and L4 show Photuris larvae under a piece of glass cover slide set upon a piece of dog hair. This species of Photuris larvae appear to aggregate and do not appear to be very aggressive at this stage. L5 is a Photuris larva which is slightly increased in size after feeding and moulting. L6 is a Photuris larva busy crawling around the edge of the Petri dish. Photo © 2010 by Terry Lynch.

Fig. 9. Photuris larvae between glass cover slip and soil. Photo © 2010 by Terry Lynch.

In Fig. 9 a Photuris larva is shown after it crawled between the glass cover slip and soil. The glass cover slip provides a secure crevice for the Photuris larvae to aggregate while still enabling them to be observed. This is a technique that I have also used with Photinus pyralis larvae. Photo © 2010 by Terry Lynch.

Fig. 10. At ten days old a 2.48 mm long Photuris larva is seen here feeding upon a small earthworm. PHOTO © 2010 by Terry Lynch.

Five Photuris larvae were observed under the cover glass some eleven days after the first larvae emerged from eggs. This again confirms that this species of Photuris larvae tend to aggregate during the early stages of development. Also several areas were observed in the soil where larvae had made holes and disappeared under the soil. One small larva which had previously been found atop the cover glass was immobile and expired, a state which has remained such for some seven days. I'm not sure why this larva expired; perhaps it was bitten by another larva or just had something wrong with it. At least four of the larvae that emerged from eggs expired.

Rearing firefly larvae may be both a fun and educational challenge. In this respect I would like to challenge those who enjoy studying fireflies to the following tasks:

1. The Photuris firefly larva shown above began to emerge from eggs in 17 to 18 days from the time the female firefly was captured and set in a jar with moist, sterile soil. It would be a challenge to try to make a time lapse video of firefly larvae emerging from eggs. Try to collect a 12 to 24 or more firefly eggs, put them together in a cluster, and make a time lapse video of larvae emerging from eggs. By using a cluster of eggs and making a time lapse video that begins when the larvae are about ready to emerge from their eggs, one may have a good chance of recording emergence.

2. How long do firefly larvae take to fully develop? How many times do various species of firefly larvae moult before they emerge as adults? Most species of firefly larvae have not been studied. What factors determine the rate of growth of firefly larvae? How does the rate of growth of firefly larvae vary with temperature and food type? Note that the rate of growth of firefly larvae may be a function of temperature such that firefly larvae in warm climates may develop very rapidly and go through a number of generations in a year, whereas those in more northern climates may go through only one generation in a year or two years. This presents an interesting challenge: rear firefly larvae of various species from different areas. Determine what foods the larvae will eat to promote their growth. Determine the number of times firefly larvae moult. Determine the rate of growth by measuring their size and/or weighing the larvae stages after each moult. Also determine how long it takes for different species of fireflies to develop from emerging from egg to emerging from the pupae stage to an adult firefly. Note that in tropical areas as Jamacia, fireflies may develop very rapidly and go through a number of generation each year; hence, these would be very good fireflies to rear. In the deep south, as in Florida, where the soil is warm and does not freeze, firefly larvae may go through one generation in a year. In northern climates where there are cold winters firefly larvae may require two years to mature. Certainly because most species of fireflies have not been reared from egg to adult this represents a challenge and opportunity for aspiring entomology students.

3. What do firefly larvae eat? I have observed Photuris larvae eat fruit flies and kibbles (moisten dry dog food). I have observed Photinus pyralis larvae eat earth worms. Firefly larvae have also been observed eating snails. It would be interesting to test various other foods to see what firefly larvae will eat. For example, will they eat fresh chicken or other meats? Will they eat other expired insects? Will they eat fly maggots? After hatching firefly larvae from eggs provide test samples of various foods to see what firefly larvae will actually eat.

4. Can firefly larvae be found inside small snail shells? The fact that firefly larvae eat snails may suggest that firefly larvae can be found inside snails. Many very small snails live in soil where firefly adults are observed. The challenge would be to collect soil samples, sort through the soil samples very carefully with a magnifying glass, and collect small snails and their shells. Then set these to rest and examine the in complete darkness. Disturb the snails and snail shells while watching in absolute darkness. Will any of the snail shells exhibit an alarm glow as a result of a sharp vibration? If so this would indicate the presence of a firefly larva inside the small snail shells. Try to collect hundreds of tiny snail shells from soil samples in different areas where adult fireflies are observed and glow test them. Can you fine snail shells that contain prey firefly larvae? If so please let Dr. Firefly know of your finds.

5. What artificial food mixes will firefly larvae eat? The fact that Photuris larvae have been observed eating such artificial foods as moist kibbles (dog food), indicates they it may be possible to formulate an artificial food that is ideal for firefly larvae such as Photuris or Photinus. Try to formulate various artificial foods and test feed Photuris larvae. Perhaps an artificial earthworm can even be made which could consist of a mix of different ingredients. For example, combine egg yoke, powdered milk, fresh chicken broth and agar-agar; heat this mix to boil for 30 minutes and take into a syringe. Let cool. Then squeeze out into small tubes to make artificial worms. Another "artificial worm" might contain a mix made from actual earthworms that is ground in a blender with water and agar-agar, then boiled for 30 minutes. Again take the sterile mix into a syringe and when cool squeeze out tube worms to test feed firefly larvae. It should be possible to come up with an ideal artificial tube worm that firefly larvae love and will readily eat using this method.

6. Firefly larvae glow when alarmed. It would be a challenge to try to photograph larvae using their own glow. Hatch about 12 to 24 firefly larvae from eggs. Then cluster the larvae together, as in an impression of moist clay soil covered with a glass cover slip. Let set undisturbed. Then try to photograph the larvae glowing brightly after they are disturbed. Larvae may also cluster around food and then be made to glow with a gentle puff of air or by making a vibration. I'd love to see some really close-up photographs of early instar firefly larvae glowing.

7. Adult female Photuris preys upon Photinus and acquires toxins which may aid in survival of the adult fireflies. The question is, do these toxins pass to the eggs and larvae, and if so, do these passed toxins aid in the survival of firefly eggs and/or firefly larvae? The challenge is to determine if toxins which occur in Photinus adults are found in Photinus eggs and/or Photinus larvae which newly emerge from eggs. Do Photinus larvae manufacturer these toxins? What about Photuris larvae? Do Photuris eggs or larvae contain toxins? If so, at what levels or concentrations? Is it possible that the glowing of firefly eggs and firefly larvae serves to signal that the eggs and larvae are toxic to predators? Try to feed firefly larvae to prey such as spiders or ants, to see if the firefly larvae are rejected.

8. What role, if any, do the zig-zag,. sawtooth, shark fin-like segments of Photuris larvae and their long hairs play in survival? It would seem that these long hairs would be ideal for detecting vibrations, alerting the larvae to flash in alarm, prehaps to warn pray that firefly larvae are toxic (perhaps Photuris larvae even mimick more toxic Photinus larvae). Do the zig-zag, sawtooth, shark fin-like segments make Photuris larvae hard for some small animals, like frogs, to swallow? Do spiders, frogs or other small animals reject eating Photuris larvae more or less redially then they reject eating Phitinus larvae? How does rejection of Photuris and/or Photinus larvae by spiders, frogs or other small animals relate to the level of toxins in firefly larvae blood? Does the alarm glow of Photuris larvae when they are disturbed, cause them to be rejected by small animals which have previously fed upon either Photuris and/or Photinus adult fireflies and/or firefly larvae of same or different species? These questions represent a challenge for future investigators.

9. Fireflies have been mentioned in literature and may serve as inspiration for the creation of art. I have produced many gift and apparel items which feature fireflies. I would like to challenge others to do the same. Can you make photographs of fireflies and/or their larvae and turn them into art? Shown below is a work entitled "Firefly Goddess" created from a photograph of a Photuris larva.
   
   Firefly Goddess. Buy these Firefly Goddess gifts and apparel featuring a pradaceous Photuris firefly larva.

   Fireflies and their larvae may serve as great inspiration for drawings, paintings or other art. In recent years they have been used in movies themes and commercials. Should you create an original work inspired by your fascination with fireflies please post it on-line and send a link to Dr. Firefly.

There are many experiments which can be performed upon young firefly larvae. Very little is really known about firefly larvae. Collecting firefly eggs from adult females, incubating them, then studying the emerged larvae makes for a very interesting challenge. Can you suggest any other experiments for firefly larvae? If so please send them to Dr. Firefly. I would like to hear of anyone who rears firefly larvae from eggs and conducts any original experiments upon the firefly larvae.

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Firefly Goddess. Buy these Firefly Goddess gifts and apparel featuring a pradaceous Photuris firefly larva.

Firefly Wheel of Fortune. To the critical thinker fireflies bring to mind many issues as illustrated by the Firefly Wheel of Fortune. This design features a rosette of golden Photuris firefly larvae. Photo and graphic by Terry Lynch, naturalist.

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