Firefly Mysteries Masthead

Firefly Mysteries

by Terry Lynch
1 July 2001


Firefly Mysteries presents revelations related to the rearing, egg, embryo, early instar and behavior of Photinus pyralis larvae with respect to gregarious feeding behavior, vivisection of host food via digestive enzymes, interring of earthworms and proof larvae use eyes and lanterns to form aggregates. This report is a challenge for investigators with emphasis on the role firefly larvae may play in research into the genetic key codes which link and differentiate flash pattern to species.

P. pyralis mating
Figure 4. P. pyralis female perched at apex of pine tree twig rising from forest floor as male mounts and copulates with her. The male and female were locked together as female released from her perch when disturbed them to make capture. The male turned around to establish the pair was copulated. However male and female disengaged while handling to make capture. This same female later was placed in a jar with 7 freshly captured males and copulated for a second time on the same evening. Hence females will copulate more than once per evening if disturbed to cause a separation. The fact females of P. pyralis mate with different males on sequent nights suggest eggs are fertilized by different males; hence this intensifies competition among males to copulate and pass their genes on to the next generation.

The Challenge

As the above picture illustrates, fireflies are a very competitive species. The first firefly to find and locate a female is the one which gets to mate and pass its genetic material to the next generation. Researchers of fireflies as well as many other disciplines are also a very competitive species, often preferring to work alone and hoard the fame, fortune and glory of their discoveries. When taken to the extreme this process results in universities and departments competing for grants and limited research funds. The result is that many research projects die before they see the light of day, never making it off the drawing board. Also, humanity, I believe, suffers from this process, in that discoveries which might be enabled by cooperation and group effort, go unmade. Wouldn't it be marvelous if researchers would set aside their greed and work together on a frequent bases to share their knowledge and enable a more rapid and through understanding of our natural universe! In this regard I challenge scientist to work as teams to uncover the mysteries of firefly behavior.

Unsolved mysteries related to firefly behavior

Fireflies exhibit a number of mysterious behaviors beyond their mere flashing. Although recent reports give insight into how fireflies flash, there remains many unanswered questions related to fireflies and their behavior.

Having studied fireflies for over 30 years their complex behavior continues to amaze me. Most people fail to realize that there are hundreds of species of fireflies and that fireflies live the majority of their life as larvae, unseen and hidden from the casual observer who is dazzled by the summer time courtship flight of short lived adults.

What makes one genus-species of firefly differ from another is perhaps the greatest mystery of firefly behavior. It has been established that adult fireflies use complex signaling pattern in their courtship but the nature of these complex flash patters, though described for a number of species, remains mysterious. In fact we hardly understand what makes one genius of fireflies differ from another, much less how the numerous species encode and modulate their distinctive flash patterns.

Study of firefly larvae emphasizes that the difference between the various genus of fireflies includes extreme variations in morphology at the larva stage. Although differences in genus of fireflies carries over to the adult forms, morphological differences between the various species often becomes vague. One firefly species may so resembles another that only their flash patterns can distinguish two different species (See James E. Lloyd's work in describing the flash patterns of a number of species of fireflies).

P. pyralis mating
Figure 1. The novice who is just beginning to learn to recognize fireflies may wish to note the difference between males and females of the species P. pyralis. Females are somewhat larger than males which have a large lantern and fly about in search of females which are generally perched upon a leaf, twig or even a tree trunk. The female has a much smaller lantern than the male and will flash in response to seeing a male. There is a delay of approximately 2.0 seconds between the male flash and a female response in this species. This fact can be used to hunt for females by flashing a pen light to mimic a male's flash pattern. The ability to hunt for and capture females makes P. pyralis and ideal species for the study of mating, egg collection, larvae rearing and related studies.

As structure is linked to genetic code, the key to each firefly's organization and presentation of structure may be viewed as an unknown code. The nature of this code from species to species also holds the key to why each species flashes with a unique pattern used in its courtship behavior. Identifying and reading this code remains one of the greatest mysteries related to firefly behavior.

The study of firefly larvae presents an opportunity to explore in greater depth the factors which cause differentiation of genus and species. This is because all the genetic information expressed in adult fireflies is contained in the larvae. Although we may not yet know how to read or decipher that information it is still locked in the genetic code of firefly larvae.

One of the problems then, is obtaining firefly of known genus and species for research; i.e., of known parentage. The methodology for securing I-instar firefly larvae has basically been worked out. One of the significant results which should follow is that a number of larvae from known parentage may be secured for genetic analysis. By making comparative genetic analysis of larvae from say P. pyralis

and Photuris sp. one may begin to decipher the differences in genetic code which characterize how the genus vary apart from variations in individuals. Applying these same methods to several varieties of Photinid will begin to reveal genetic code variations between species. Hence working with firefly larvae, rather than adults, may prove very fruitful.

P. pyralis mating
Figure 2. Egg collection chamber with P. pyralis copulating. The female in the background was temporarily catatonic and resting after having been linked with male approximately 4 hours and handled rather roughly in transferring to egg laying chamber.

Figure 2 above illustrates a simple egg collection chamber for obtaining I-instar P. pyralis larvae. Adult females of the species may be located in the field by using a pen light to pan the search area. When one mimics the flash of males (panning an area each 5-6 seconds to produce a short flash), females perched on the ground or vegetation will respond in approximately 2 seconds. I've used this method repeatedly to collect numerous female P. pyralis, generally occurring in the early summer (June-July) in central Alabama. Then it simply is a matter of placing the females in a jar with males to permit copulation. Once a female copulates, which may last 2-4 hours, they are set in egg collection chambers where they deposit eggs.

P. pyralis eggs collected by T.A. Lynch
Figures A and B. In Figure "A" eggs are shown deposited by female P. pyralis 1 - 5 mm beneath surface of soil. Eggs are also deposited on top of the soil as seen in Figure "B" with a number of clumps of eggs and single eggs shown around several expired fireflies. This photo was taken nine days after three female P. pyralis were placed in the egg collection chamber.

Females are maintained in egg collection chambers with males and allowed to copulate with males each evening or as may occur. The females then deposit their eggs over a course of days. Just before larvae are ready to hatch from the eggs, sharp vibrations will cause the larvae inside the eggs to glow brightly. After about 14 days young I-instar larvae will begin to emerge and may be collected for study.

If you are interested in the rearing of fireflies and/or behavior of early instar firefly special galleries have been provided for your review. To see developing eggs which have been photographed under a variety of lighting conditions please visit the Egg and Embryo Gallery. Behavior of early instar larvae is illustrated and recorded through a series of dymanic photographs in the Firefly Larvae Gallery.

Firefly Egg and Embryo Gallery

Firefly Larvae Gallery

The above described procedure for collection of P. pyralis eggs and larvae also works to collect I-instar larvae from Photuris sp. However the collection of adult Photuris usually involves scooping them out of the air as they flash or locating the blinking females flashing upon the ground. Both the male and female of Photuris readily fly and may be netted. The females of Photuris are easily distinguished from the males by their pointed posterior abdominal segment and ovipositor. Another interesting behavior of Photuris is that the female will attract males of P. pyralis by mimicking the flash response of a female P. pyralis. Then the female Photuris will devour the male of P. pyralis, eating them alive! This aggressive mimicry was first described by James E. Lloyd. Photuris females will also eat male Photuris which may enhance the egg laying of female Photuris, given a well fed female has the nutrition required for good egg laying. Also Photuris females readily lay eggs when placed in jars of sand or soil and the emerging larvae seem to be scavengers, so may be more easily reared than P. pyralis, which may be host specific.

P. pyralis mating
Figure 4. Firefly orgies are common in the field or in the laboratory when several males locate a female and compete to copulate with her.

Figure 4 shows a typical firefly orgy. Generally when a female P. pyralis is placed in a mating chamber with more than one male, there is competition for the female. In the field this behavior may also be observed and involves several males attempting to recognize the female and copulate. Yet males will continue to attempt copulation, probably aroused by pheromones. In fact anyone who has spent much time collecting quantities of P. pyralis can tell you these fireflies have a distinctive bitter taste and rather poignant odor. These pheromones have been reported to have a protective role as small animals do not like the taste of fireflies and will often refuse to eat P. pyralis. Also the female pheromones seem to drive the males nuts! Males become so aroused by the female that they even try to copulate with other males -- or at least this is the impression one gets. Actually males all are trying to copulate with the female and they poke and probe with their posterior genitalia seeking a union even after a female has already copulated with another male. I've little doubt this behavior may have contribute to both the length of a male firefly's body and penis, that long protruding hairy hook which males extend around and about other males when vying for a female's attention.

P. pyralis mating
Figure 5. Larger female pulls male so she stays facing upward on leaves, stems, twigs, tissue or clinging to a slick glass surface. If female is disturbed she may exhibit a catatonic reaction, falling from the perch. This behavior enables the pair to escape predation.

Figure 5 illustrates a pair of P. pyralis resting while copulating. Copulation generally lasts for 2-4 hours. The female being somewhat larger than the male will drag the male around to find a new perch should this be required. Walking up stems or leaves the copulated female may escape the attention of other males. Once copulated a pair remains oblivious to what's going on around them. The attentions of other males are ignored. One may tap or knock upon a jar containing a copulating pair and these vibrations do not seem to bother the pair. They may even be gently moved or handled upon a small twig, stick or straw, as when transferring from one container to another, without disturbing the copulation. However if handled too roughly, especially in the wild, the female may become catatonic and/or fall from her perch. By "too rough" I mean trying to pick up the copulating fireflies or to hold or grasp them. Such rough behavior may signal a defensive response, such that the female tries to drop or fall and escape or in the case of a female that has completed copulation, she may actually become catatonic.

After copulation the female may rest or if handled too roughly she may become catatonic, feigning death. This catatonic state is apparent when the antennae become limp! Apparently the blood in the antennae is sucked out so that the antennae become loose and flimsy, without any rigidity. A catatonic female will remain motionless for many minutes before rigidity is restored to her antennae by pumping blood back into them. Generally I have observed this behavior only when handling a female too roughly.

Obviously this catatonic behavior so evident in a female which has just copulated and is handled is extremely beneficial to the survival of the species. A female which has copulated carries both sperm and eggs and her sole mission in life is now to fertilize and deposit those eggs. Toward this end the female will become catatonic and feign death if disturbed too roughly, which probably protects the female from spiders or other predators. This behavior also explains why a female will loosen its grip on a leaf or twig in the field when one is collecting them. By becoming catatonic a female will fall to the ground and escape capture by large rough handling predators or people trying to collect them. This has been my experience in collecting females such that the method I use is to let the female drop into a net, jar or other collection vessel. Generally females may first try to escape, burrowing to hide in leaf litter; but if the male and female become separated and one picks up the female, squeezing or holding it, then when set down she may feigne death for many minutes.

Egg laying is a process which occurs over a period of days. Having copulated a female will deposit her eggs in the soil, probing with her ovipositor into the most minute of cracks and crevices. These soft eggs soon harden into tiny pearls which glow! In fact over a period of some 14 days as the larvae inside the eggs mature, the eggs will become responsive to vibration and glow very brightly when a sharp vibration occurs in their vicinity. This may be observed by setting a Petri dish of firefly eggs on a a table or counter top in a completely darkened room. Then after letting one's eyes become accustomed to the darkness, tap the Petri dish. The larvae inside the eggs will glow brightly. This is best observed a day or two before the larvae emerge form the eggs.

I first observed this firefly egg glow due to vibrations in 1968. After collecting numerous eggs, putting them in a Petri dish with moist tissue and letting these rest undisturbed, they were observed daily. Several days before the larvae emerged the eggs were observed in complete darkness. A light tapping upon the Petri dish caused a bright glow which then faded. This indicates that larvae inside the eggs have matured to the point of being able to take in oxygen and flash their lanterns when their nervous system detects vibrations.

When firefly larvae emerge from eggs they are white, not having yet taken upon a darker coloration. Photomicrography of such tiny larvae enables one to easily see the internal structure of larvae without need for intrusive dissection. Simply place the colorless, transparent larvae upon a microscope slide in a drop of water, lay a cover slip over the larvae and observe it under various powers of magnification. Using this method one may explore the various morphological variations between the genus-species of various fireflies in their larvae stages. These young larvae should also be an invaluable resource to genetic researchers searching for the code keys linking flash behavior to genes, for firefly larvae of common parentage and of known genus-species are the only source of genetic material that is identical, from individual larvae to larvae, such that this enables repetitive comparative analysis of DNA.

Key questions for future research

Although I have not been fortunate enough to enjoy access to a well equipped laboratory or the resources to support an in depth, expensive investigation into the nature of firefly flash key codes, by which I mean those genetic chains of DNA which describe the flash patterns which link and differentiate species, it is clear firefly larvae research might yield a wealth of information in this respect. Some of the questions which may be answered are:

  1. How are flash patterns linked to genetic code?
  2. How does the flash pattern genetic code key vary from one genus-species to another?
  3. How does altering or changing genetic code keys as indicated by variations in genetic key codes change resulting flash patterns or modulation; i.e., how is behavior linked and determined by genetic key codes?
  4. Specifically what part of the genetic code is responsible for determining the difference in behavior between genus-species and the various morphological differences between genus-species?

Significant observations and discoveries

If the study of firefly larvae may help answer these fundamental questions, certainly more time, effort and resources should be devoted to this topic. As an amateur naturalist and firefly researcher working out of my suburban laboratory (See Figure 5) I've made a number of significant first time observations and discoveries. These include:

  1. First person to collect and rear P. pyralis from egg to larvae in large numbers.
  2. First person to witness vibration stimulated glow of mature P. pyralis larvae inside eggs.
  3. First person to make photomicrographs of I-instar P. pyralis and I-instar Photuris larvae for comparative analysis
  4. First person to note the morphological significance of P. pyralis larvae vs. Photuris larvae as relates to diet of P. pyralis larvae.
  5. First person to use ether to enable collection of firefly larvae in the field.
  6. First person to observe alert/rest preflight behavior in P. pyralis males. This was reported to Dr. James E. Lloyd and John Bonner Buck. Buck later confirmed the behavior in another species of Photinid.
  7. First person to describe vivisection of earthworm feeding behavior of Photinid larvae.
  8. First person to record the effect of honey on the longevity of adult male P. pyralis (see Figure 6).
  9. First person to record the effect of wolf spider attack and venom injection upon the flash rate of P. pyralis.
  10. Developed numberous original techniques and methods for usage in the research and study of fireflies and other insects.
  11. First person to make digital photomicrographs and enhancements of P. pyralis eggs, embryo and I-instar larvae.
  12. First person to observe, photograph and prove that P. pyralis early instar larvae eat earthworms.
  13. First person to observe and photograph cooperative group feeding behavior, vivisection, interring of earthworm, and lair construction by early instar, gregarious P. pyralis larvae. This behavior, like that of preflight behavior, is most probably characteristic of all Photinids and should therefore be observed in other species of Photinids.
  14. First person to suggest that firefly behavior in larvae and adults, especially with regard to gregarious behavior of Photinus pyralis vs. aggression in Photinus and species specific flash communication, establishes the mythology of divine creation, given variations in behavior can not occur unless one behavior exist before another, negating the argument of creation and proving beyond a reasonable doubt that evolution occurs.
  15. First person to prove that early instar P. pyralis larvae use their lanterns and eye sight to form loose aggregates via Lynch's Lantern Function Test, a controlled experiment which compairs tendency to cluster in the absence and presence of light.
  16. First person to finally established the full sequence and range of complex behaviors, specifically of the larva stage of P. pyralis, giving full insight into the life cycle of this species from egg, through larva, pupa and adult, that in the future this may enable rearing of fireflies and genetic or behavior research to reveal even more mysteries of the firefly.

P. pyralis mating
Click on pic to contact Terry Lynch

Figure 6. Suburban entomologist in Desert Storm camouflage writing firefly journals with microscope, red insect net, specimen bottles, paraphernalia and inquiring mind, everything needed to explore the back yard jungles of American suburbia.

New horizons

I've often wondered what other discoveries I might be able to make had I the time and resources to devote my full attention to the study of entomology and animal behavior? Should any university wish to offer me an honorary doctorate and position to pursue such research, I would certainly consider this a well earned opportunity. Also I will accept donations and grants to support my firefly and entomological research. In fact, I'd like to build a natural history museum and science research center one of these days. If you would like to contribute toward this effort you may make a donation via PayPal. Simply click on the PayPal button below, set up your account and then make your secure payment using your credit card or a bank transfer. Thank you.

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In addition I will accept any gifts of laboratory equipment or supplies including computers, photographic equipment, microscopes and reagents. People who would like to contribute firefly specimens should contact Terry Lynch. I am in special need of living female fireflies from around the United States. I would also like to obtain living aquatic males and females from the orient. In addition I would like to obtain any books or reference materials related to entomology which anyone may have which they would like to discard. I'm especially interested in a first edition of the 10-volume Souvenirs Entomologiques by Jean Henri Fabre, English translations of Fabre's work and back issues of Scientific American, especially those with articles on insects and/or bioluminescence.

It should be seen from these considerations that fireflies remain some of the most mysterious and wondrous of insects. Much remains to be learned about them. Recently it was discovered that the flash of Photuris sp. is triggered by the release of nitric oxide when a signal is sent from the firefly's brain to its lantern. Yet we still don't have much of a clue to what goes on inside the brain of a firefly. Nor do we know how that tiny little firefly mind controls its flash patters and how this is linked to code keys in strands of DNA. Clearly there could not be a more compelling area of research for teams of eager scientists with the systems and resources, plus the brain power, to attack these problems. Should this come to pass in my lifetime, I might gladly contribute some effort to providing a few P. pyralis firefly larvae.

P. pyralis males eating honey
Figure 7. P. pyralis males gorging themselves on a drop of honey as it runs down the inside of a jar. Adult fireflies in captivity live longer when fed honey than control groups fed only water. This enables one to maintain living specimens for observation and experiment slightly longer than would otherwise be possible. Honey may also enable female fireflies to live longer thus increasing the yield of eggs and young firefly larvae. Feeding fireflies honey to extend their adult life is not so unusual if you consider the fact that adult fireflies, especially tropical species, may drink nectar from flowers. Some people even profess that honey has healing properties and that eating royal jelly can extend their life span. Of course there are people around the world who will eat just about anything believing it will make them healthier, sexually potent or extend their lives. In reality the unbalanced, fad or junk food diets of many people probably contributes to their early demise. Of course it is a misconception that fireflies do not live long in nature. From egg to larvae, pupae and adult is a process which takes at least a year, perhaps longer in colder climates. Firefly studies may not ever contribute to the longevity of people but they sure do contribute to the joy of life and provide a challenge for all inquiring minds.

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The following firefly presentations by Lynch may also be of interest:

Other Lynch Sites

Project K9 | Blinks and Links | The Urban Jungle | Firefly FAQs | The Amateur Naturalist | Firefly Notebooks | Feeding behavior of Photinid larvae | Flash Keys in Fireflies | Contact the author

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Home | Introduction | Firefly FAQs | Blinks and Links | Eggs and embryo | Early Instar | Firefly Art | Evolution | Flash Keys in Fireflies | Firefly Notebooks | Photuris | Contact the author

Copyright 2001-2005 by Terry Lynch. All Rights Reserved. Please give credit where credit is due. If you want to use any of the photographs on this site as to publish them in books, articles or other web sites, please ask the author for permission. Also, this site is a report of original research, observation and experiment conducted over a period of years by the author. In any related investigations please site the author's works just as you would had it appeared in a scientific journal. Thank you.