Firefly head. Photuris sp., female, collected by Terry Lynch in Quitman, MS. SEM Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Note: This image has been digitally enhanced and manipulated and does not represent the true colors of a firefly.
Firefly head. Photuris sp., female, collected by Terry Lynch in Quitman, MS. SEM Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Note: This image has been digitally enhanced and manipulated and does not represent the true colors of a firefly.
Shown here is a SEM of the head of the firefly, Photuris sp. collected by naturalist and photographer, Terry Lynch, showing special and distinguishing features which may represent special adaptations with respect to its predacious behavior.
At "A" is a grooved mandible. Photuris has two very large grooved mandibles which inject very caustic digestive enzymes into its prey which are Photinus fireflies. Photuris bites Photinus and injects digestive fluids which quickly liquify its prey; they Photuris sucks up the liquefied flesh through its mouthparts. Hairs around the mouthparts filter out debris.
At "B" is seen a special adaption to the cuticular structure or labrum between the two grooved mandibles in the form of three sawtooth-like projections; i.e, in this species of Photuris the apex of the labrum is trilobed with three lobes or teeth. These may functions like a saw and enable Photuris to quickly kill its prey, Photinus, and aid in ripping apart the flesh of Photinus as it is devoured and ingested. Observations of the female Photuris show that it lures its prey by mimicking the flash response of a female Photinus. When the Photinus firefly lands next to Photuris, the larger Photuris quickly jumps upon Photinus and presses its head under the pronotum of Photinus. Photuris bites Photinus and a right to left motion of Photuris causes it to cut into the flesh of Photinus and sever nerves, paralyzing Photinus. Then Photuris may leisurely proceed to rip Photinus apart, turning its flesh to liquid, and sucking up the liquefied flesh over the course of the evening. Photuris is genuinely the "vampire" of fireflies!
At "C" is seen a curious adaptation at the base of the antennae socket which resembles a heart such that the cuticular structure around the base of the antennae indents into the antennae which bulges inward. Because antennae are used as feelers and are sensitive to vibration, this morphological adaptation may be the result of the predacious behavior of Photuris. The antennae of Photuris are probably very important in sensing the presence of Photinus. Photuris has an arched body which causes its head to be pointing at an angle downward, such that antennae would tend to be pressed downward. Hence Photuris would be in an ideal stance to sense the vibrations and presence of Photinus when it alights near Photuris. Also Photuris are able to make aerial assaults upon Photinus or other species of fireflies, literally colliding with prey fireflies, latching on to them using their tarsal claws and sticky tarsal pads. Antennae and appendage position of Photuris in flight may be a factor worth investigating to determine if it may have any bearing upon morphological adaptations. In any case, the "heart shaped antennae" cuticular structures are NOT a symbol of affection in this case, but rather a result of the a morphological adaptation which has the result of making Photuris a better predator, able to feel and sense the presence of its prey, and much like a spider senses vibrations, to detect its prey, leap upon it and kill it with a quick bite and sawing action beneath its pronotum.
The pronotum "D" of fireflies certainly serves as a protective shield given it is the soft tissue area beneath the pronotum and around the head of a firefly where the voracious Photuris attacks its prey, severing nerve fibers to paralyze its victims. Hence fireflies have adapted to have large pronotums as a defense against predation. Also the large pronotums shield light from above the firefly's head, be it from the moon, stars or other sources. Thus this shades the eyes and perhaps enables fireflies to more readily see its mates upon the ground or perched upon vegetation.
Certainly the large spherical compound eye "E" of fireflies is an adaptation of great aid in locating a mate. Photuris is a rapid flying firefly and may speed rapidly over fields and meadows seeking a mate or even fly high over wetlands and in tree tops flashing in search of a mate. Large compound eyes enable a firefly to locate its mate from a distance and help avoid collisions at low ambient light intensity levels. The two large compound eyes of fireflies are certainly one of Lampyridae's most significant adaptations which enable it to locate both its mate and prey fireflies both which respond to flash singles produced by the firefly's lantern.
Naturalist Terry Lynch collected, preserved, provided, identified, and described this firefly specimen. Lynch had SEM images made of the firefly's compound eye and other structures which he digitally enhanced to illustrate the firefly's amazing structures. Fireflies use their large compound eyes to locate mates as they fly and flash during twilight and evening hours.
The body structures of Photuris fireflies and other species of fireflies are well adapted to use in what Lynch calls "Firefly Warfare," the competition for territory which represents a food source. When some species of fireflies have come to dominate a region and increase in numbers such that they occur in very high population densities, they are able to establish synchronous flashing. Those species of fireflies which have evolved to be most successful in totally dominating a territory are the most probable to exhibit synchronous flashing.
The concept of "Firefly Warfare" reflects the true nature of Lampyridae as a family of many different species and tribes of fireflies which are involved in constant competition for territory which represents a food source for firefly larvae. The idea that fireflies are gentle creatures illuminating the warm summer evenings with festive, romantic flashes, to entertain and delight we humans, is but a fallacy and myth! Fireflies are a highly evolved species engaged in a constant battle, in competition to rule the night skies and gain power and control over as much territory as they can for the benefit of their particular species. The flashing behavior we see exhibited by fireflies is not simply their mating signals, but a form of communication that establishes a social network of waring fireflies in a constant battle to rule the night!
Enjoy reading these original articles and reports about fireflies by Terry Lynch who has long enjoyed spending his summer evenings watching the dance of fireflies in fields, meadows and forests. Lynch has been studying fireflies since he was a teenager and lived at the edge of Talladega National Forest in Jacksonville, Alabama, where Photinus pyralis occurred in such great numbers one could easily net hundreds in the course of five or ten minutes. Today such large numbers of firefly have decreased in many areas due to the impact of urbanization, over spraying for mosquitoes, light pollution and other factors. Learning about fireflies is the first step in preserving them that our children's children will still be able to enjoy watching fireflies twinkle and flash during their twilight mating dance each summer.
The Firefly Gallery Help save the firefly! The proceeds from these charming design items will be used to support firefly studies and research and advocate preservation of the environment and fireflies.
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Credits: Specimens of fireflies collected, preserved, identified, described, and provided were imaged by Dennis Kunkel of Dennis Kunkel Microscopy, Inc. Any usage of these images requires prior and written permission of the owner/s.