Presented by Terry Lynch
4 July 2001
An enlightening and humorous treaties upon the marvels of fireflies behavior as it relates to the nature of humanity
They fly through the night, softly, gently, gliding over hill and dell, watching with spherical, multi-faceted eyes, surveying all the country side. Hovering they pause briefly, as if to peer and ponder, then they rise and fly leaping through the night only to dip toward the earth and suddenly flash, then hover, then take a flying leap and flash again. Over and over they process is repeated by a thousand, thousand dancing lights and watching eyes. It is the courtship flight of Photinus pyralis, more alien than alien, one of nature's most marvelous insect miracles, surely as wondrous as any fanciful visitors from outer space or extraterrestrial creatures of Hollywood. Yet few people give the firefly more than a glancing notice as children; something of its wonder lost upon maturity, or is it that we have forgotten how to see least it be to watch the one eyed monster of a glaring television screen?
Fireflies are common throughout much of the south and eastern United States east of the Mississippi River. They occur in numerous tropical and subtropical ecosystems where they may sometimes be observed in great numbers. Each of the hundreds of species of fireflies has its own unique flash pattern which together with its flight behavior combines to make a courtship dance. Yet we know relatively little about fireflies even though they have been studied by some of the brightest minds in entomology. I say this having poured over much of the professional publications related to fireflies. Also I have pondered their mysteries for over 30 years! Yet still no one knows how one species of firefly flashes in the characteristic, species specific manner it does while a closely related species flashes in a different pattern. The answer to this question seems locked inside the firefly's tiny brain and DNA code. It is every bit as mysterious as the process of complete metamorphosis which changes a firefly larvae into an adult firefly every bit as different a creature as a maggot if from a fly or a caterpillar is from a butterfly!
In pondering the mysteries of species differentiation of fireflies, the firefly larvae is a good place to begin. In every species of firefly larvae is encoded that set of behaviors an adult will exhibit which will make it flash and fly with a unique courtship dance through the twilight sky. Yet firefly larvae of similar species look outwardly similar. But are they so similar as to be indistinguishable if minutely studied?
When I first collected I-instar firefly larvae of P. pyralis (See Firefly Notebooks: 1968-1970), and observed them under a microscope, I noticed that they have very prominent hair structures. It is possible these hair structures may be specific to species. Also it is possible, even extremely probable, that each species of firefly larvae has a unique genetic code, one which can be keyed and compared to that of the adult firefly, such that once this is done for many species it will be possible to identify firefly larvae by species just from their genetic code.
Of course using genetic code to identify firefly larvae, or the species of any insect for that matter, may be cost prohibited at this point, given the fact that it is usually an expensive proposition to make even simple genetic analysis. But I see no reason why this may not be done in the future as costs come down, especially if present researchers establish this as a goal. One of the significant advantages of using genetic keys to identify firefly species it that it should enable differentiation of species, as in the case of Photuris, which currently is very difficult, if not impossible to do from specimens unless one has living specimens captured in flight after recording their flash pattern.
As a naturalist who pursues the study of fireflies and other insects from my back yard laboratory, without the aid of grants or any sponsorship through universities or other academic association, the funds for making any genetic analysis of firefly DNA are nonexistent.
Figure 2. 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.
However, I do recognize the fact that recent advances, such as the human gnome and the canine gnome project, might reflect technologies which could be applied to the study of fireflies, other insects and, in fact, all small animals. However, my own resources permit only that basic research which cost nothing and is entirely funded by keen observation, deductive reasoning and the love which is expressed through meeting the challenge of an intellectual problem.
In this respect firefly research is much like trying to solve a mathematical equation which has as yet no solution. Indeed the genetic key codes to behavior are unsolved mysteries, cyphers which we as yet are not able to decipher. Yet in fireflies and other insects which exhibit preprogrammed, unlearned behaviors, it is easy to deduce that such behaviors are genetically encoded, for the genes determine a firefly's entire structure, its entire molecular arrangement of body and form; such that, as function and behavior follows form form, the flash patterns characteristic of fireflies must be the result of genetic key coding. In the case of fireflies flash patters and courtship behavior is ultimately locked in the genetic code of each species. Then to decipher that code is to ultimately understand how fireflies of different species flash with unique patterns.
This theory might be tested by transferring genetic material from one species of firefly larvae (or fertilized eggs) to larvae or eggs of another species, which may produce an adult firefly which has a new flash pattern. Because Photuris is more easily reared from egg to adult than Photinid and because Photinid eggs and larvae are relatively easy to acquire, I suggest transplanting Photinid genetic material into Photuris eggs or larvae, in order to see how this effects the behavior, flash pattern or even morphology of Photuris. I see nothing ethically wrong with this type of research which could result in monster fireflies, as I assume they will not be released and into the wild, but end up in vials or alcohol or stuck to pens in a display case! Besides, I doubt I'll ever be in a position to have the resources to conduct such an experiment, so I offer it as a challenge to all academia. Should anyone want to give due credit for the concept, you may reference this publication or my general firefly notebooks and studies as "T.A. Lynch, Firefly Notebooks, 2001.
The types of experiments I can afford are more characteristic of those conducted by Jean Henry Fabre; i.e., situational experiments effected by changing a circumstance related to firefly behavior.
Sometimes situations present themselves which give very good clues to firefly behavior. This is the case with females of P. pyralis. These large females never seem to fly. In the field I have always observed them resting upon a perch, whether it be a blade of grass, a twig, leaf or the trunk of a pine tree. In fact I've found many P. pyralis females perched upon pine tree trunks. Although equipped with wings and able to fly, as perhaps for dispersal, females of P. pyralis generally appear to opt for a life of mating and egg laying. You might say they stay close to home and attend to domestic matters not adventuring forth to seek a mate, this being the males duty. This aspect of female behavior may relate to why some areas of the United States have never become populated by Photinid fireflies.
The dispersal of the species is largely determined by the dispersal of females and their disposition of eggs. Fireflies will come to occur only where eggs are deposited and larvae develop. Therefore if soil or other environmental conditions are not suitable for female fireflies to deposit their eggs and for larvae to grow and develop, fireflies will not become established. If pine forest and the leaf litter they provide is required for Photinids, then in areas where pine forest do not occur fireflies of this genus will not become established. If females were to go on migratory flights before depositing their eggs, then they might have dispersed and become established in areas where they currently do not occur. But as females of P. pyralis tend not to fly, their dispersal is a slow process and occurs only where soil and forest conditions are suitable for their survival.
Because female P. pyralis rarely fly, there is a good chance that when they first emerge they are observed near the area in which they live, grow and develop as larvae. This appears to be in the leaf litter of forest floors where pine trees occur.
At my home in Montgomery, Alabama, I have for years raked pine needles and debris to the edge of the fenced yard so that piles of decaying material line the base of the chained link fence. (See Figure 3).
The yard itself has no grass or other significant vegetation other than pine trees, interspersed by wild cherry, hackle berry and some small oak trees. In the summer when I collect female P. pyralis they are most readily found perched upon the chain link fence or upon twigs, leaves or plant branches near the fence. This suggests that firefly larvae are occurring in the piles of pine needles and other leaf debris which has accumulated along the fence which supports my deduction that P. pyralis larvae most readily thrive in the cryptosphere of pine forests.
Of course there are other factors which may contribute to the occurrence of P. pyralis larvae in any soil debris. If an area floods for long periods, it may drown P. pyralis larvae, given they are not an aquatic species. Areas with a loose top soil of decaying material rich in earthworms and well drained are probably most conducive to the survival of P. pyralis larvae.
When pine tree forests are destroyed to build housing areas, office complexes or shopping centers, it destroys the habitat of Photinid fireflies. Without pine trees to provide a rich soil, P. pyralis and other Photinid larvae can not survive. This is probably the primary reason fireflies have disappeared from some areas. Plus the fact fireflies do not really adapt well to concrete and asphalt parking lots, roads and highways which break up the normal dispersal via slow moving, non-flying, egg laden females which can not cope with walking across a parking lot to deposit eggs in a near by grove of pine trees.
Pine forests also provide shade which contributes to a longer period which P. pyralis and other species of fireflies may fly and court females. Quite often I've observed male P. pyralis flying in shady areas while the sun was still above the horizon brightly lighting other areas where fireflies were not yet active in their courtship flights. It therefore seems reasonable to conclude that trees of all types which provide shade, especially pine trees, contribute to the survival of fireflies through extending the time males have to locate females through the shade trees provide.
One wishing to find P. pyralis larvae merely has to search in those areas of leaf and pine needle litter where they most likely occur. One method to do this is to rake the ground on a dark or moonless night in the months preceding the time adults are due to emerge for their courtship flights. In Alabama P. pyralis adults generally occur in June - July so that larvae may be collected from January through May. Of course one may search for P. pyralis
larvae any month of the year, but I've had the best luck finding them in winter or spring. In central Florida Photuris larvae are relatively easy to find around lakes, rivers or wetlands, as is the case also with Pyractomena larvae. The reason most people never see firefly larvae is simply because they don't go into the forest at night looking for them! Plus digging through the leaf litter in total darkness isn't a proposition which thrills many people, not even die hard entomologists. The fear, I think, is that they will stumble upon a snake, spider, giant centipede, scorpion or even an alligator if one is collecting near a lake in Florida. So if you are squeamish or utterly terrified by such prospects, firefly larvae hunting probably isn't your cup of tea. Perhaps you'd prefer collecting butterflies or bird watching!
The fact P. pyralis larvae are found in the upper layer of soil and leaf litter suggest this is an excellent substrate for the collection of eggs and maintenance of larvae, at least in their initial stages of growth.
The above figure shows a simple egg collection chamber used to obtain I-instar P. pyralis larvae. One needs nothing more than a quart jar with about 10.0 cm of moist soil to collect and rear firefly larvae form eggs. And if you really want to see something alien, look at a I-instar P. pyralis firefly larvae under a microscope after it hatches out of an egg. Not only do these larva glow they have an anal appendage covered with tiny hock-like hairs which enables the larvae to cling to objects, hitch a ride upon an earthwork or snail, crawl through the soil, climb over obstacles and even clean itself off.
It is interesting that some entomologists have their doctorates in Philosophy and yet profess not to compare insect and human behavior, such analogies being anthropomorphic, as if to imply there is some great error in the deductive reasoning or other thought process. Yet as the slightest hint that any basic research discovery related to fireflies or other insects should have a medical application, the pharmaceutical companies jump on the patent pending band wagon to claim the profits for their own coffers.
An example of this is the luciferase-luciferin reaction as it relates to ATP and its conversion during the metabolic process. Apparently when the greed factor comes into play it is perfectly reasonable to be anthrophormorphic; i.e., to apply what we learn about insects human affairs. I ask, then, why not consider, at least in just, the various aspects of human and insect behavior, and learn from this comparison how to be, perhaps, better human beings, less like insects and more like the Gods we so praise and give reverence to in our various world religions.
Well, perhaps I should leave these matters to philosophers, you say ... ah, but isn't that what we just concluded some entomologists profess to be! Then why be so snobbish when one associates human and insect behavior, especially in cases where insects seem the more enlightened species than the lowly homo sapiens, who after all has only been evolving along a divergent evolutionary tree limb for a relatively short period of time. Insects seem to stop changing when they hit upon a working form, such as that of the cockroach. Humans obviously haven't gotten their genes right yet as we are slowly evolving into a more perfect being. How alien that final species will be from our present selves only a hundred thousand millennium may determine. Wouldn't it be quite remarkable if by then we too have learned how to glow and find our mates by blinking and flashing! Why there are some exhibitionists who already seem to be headed in that directions, but that's a topic for another altogether different forum!
Fireflies are certainly more alien than aliens! After all what could be more alien than an insect which flies about using complex, species specific flash pattern to communicate and identify its mate? I sometimes wish mate selection in humans were such a simple matter. Wouldn't it be nice to have a little flashing tale which could attract and seduce! There are some well endowed women who have flashing tails and in the era of women's liberation some might exclaim that many males are endowed with "tight asses."
So perhaps the signals humans use to attract and court a mate have their origins in some undecipherable aspect of genetic code which dates all the way back to a common ancestor, a link between humans and insects, from which all mammals long ago diverged. Thus we are separated from the fireflies by hundreds of millions of years of evolution. We have lost the ability to blink and glow or perhaps never developed this higher form of communication.
Who then, from a stand point of gene code and DNA sequencing as it relates to reproduction and survival is the more intelligent species, human or fireflies? If species specific flash patterns and communication in mate selection were criteria for establishing intelligence, the firefly is certainly more highly evolved than humanity. Male and female fireflies figured out long ago how to identify each other with a complex exchange of flashes of light. People haven't yet even learned how to glow! Plus the gnome of female fireflies realized long ago that as long as the species is correct, it doesn't matter what individual is the source of semen. This is why females of P. pyralis will copulate with a number of different males. Humans however let their foolish prejudice and bigotry cause discrimination in the mating process, when, in fact, semen from the male of any race or religion would adequately suffice to enable the survival of the species.
What could be more alien than a species like homo sapiens which selects its mates, often by random criteria, which has nothing to do with the survival of the species? It is humans, then, which are truly the alien species. Fireflies which use light, insects which use sound or other animals which use a combination of signaling methods in their courtship and mate selection, have enabled an effective and efficient form of mate selection which insures survival of the species. There remains randomness in the selection of individuals from among the species, and certainly there remains competition between individuals for a mate. But the over all process is efficient and, indeed, requires only identification of correct species. This is so evident and displayed by the the orgies in which male fireflies engage.
In the case of P. pyralis many males may be attracted to a single female. Which of these males the female copulates with does not matter, so long as it is a male of the same species, any male's semen will do the job. In fact females may copulate with a sequence of different males throughout the course of their egg fertilizing and egg laying adult life time. P. pyralis females are, then, some what promiscuous, as are males of P. pyralis, which will also copulate with different females on different nights. Yet the females seem to have found a way to horde males, at least for the evening. The pheromones of female fireflies are so strong, and males so intoxicated by these chemicals, that after a female copulates, it drags a male around which other males continue to try to copulate. Hence these male are dominated by the female and kept from flying off to search for another female.
When it comes to courtship and the promiscuity of fireflies relative to humans, humans and fireflies are not that different. "Alien" perhaps is a relative term, dependent upon what we perceive as being common or uncommon, both in terms of appearance, physical attributes and behavior. So you might wonder when pondering the marvels of fireflies, who is the more alien than alien species, is it man or is it the firefly?
The similarity of human's to insects was demonstrated most eloquently by the noted entomologist turned sexologist, Alfred Charles Kinsey. Indeed, at least as far as sexual behavior is concerned, human beings seem every bit as alien as insects. There is perhaps not any form of sexual behavior, not matter how odd or perverse, which humans do not exhibit. Remarkably people try to profess a kinship with God, to aspire toward some divinity, some ideal and holy master, some imagined creator of the universe, when in reality the human species is a sexual animal, more alien in its sexuality than the firefly, certainly not a species which is any higher along the evolutionary path than, say the cockroach! Why I'd even venture to say that the cockroach is a more perfect creation than humanity, for at least the cockroach has evolved a stable form, a genetic structure which has enabled its survival for hundreds of millions of years. Humanity has a long way to go to catch up with the more divine cockroach which I'm sure would claim to be made in God's image had they the ability to communicate thoughts such as humans do. But, in fact, the cockroach lacks this ability, which may actually be to its survival benefit. You don't see cockroaches trying to blow up the world or exterminate entire populations or races. Indeed, from that perspective, humanity is the real cockroach, at the bottom of the evolutionary tree, for while human survival as a species may be in doubt, it is likely cockroaches will be around to one day write our epitaph or ponder our demise as they feast upon our corpses.
Thus to those entomologist who would profess to be philosophers I'd say, if you are going to be a philosopher and study insect behavior, then please at least humor us. Get your head out of the sand of anthropomorphism and tell us how your work and insight into insect behavior may relate to human affairs. Surely insects have some lessons to teach and perhaps those lessons are at least as important as is knowing the biochemical mechanism responsible for a firefly's flash! We are all mature and knowledgeable enough to know that what applies to a firefly or any small animal for that matter, may or may not apply to man. But it is at last entertaining to relate how more link an insect some people behave than like the gods they profess to be. I mention was as it relates to army ants devouring everything in their paths. How like that is man's behavior of destroying his environment raping the forest and the land of natural resources, even preying upon his own species for whatever territorial or other gains this might bring. Indeed in terms of warfare humans have the ability to destroy the entire planet. Who, I ask, is more alien than aliens, man or insects? When it comes to mass destruction and annihilation of species, humanity certainly is the alien species!
The following firefly presentations by Lynch may also be of interest:
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 | Feeding behavior of Photinid larvae | Flash Keys in Fireflies | Firefly mysteries | Contact the author