On a summer's eve the fireflies dance in forests, over meadows, and catch the fancy of children and adults alike wherever they occur unmolested large numbers. Yet urbanization and the sprawl of concrete jungles and asphalt parking lots and roads is rapidly destroying firefly habitat. Plus the over spraying for mosquitoes prompted by a paranoid, perhaps somewhat justified, of contacting a mosquito born disease, is wiping out entire populations of fireflies. Add to that the turning of night into day by lighting cities from dusk until dawn with artificial lights, which blind fireflies and prevent their courtship over areas which were once their domain, and one has the making of an environmental catastrophic.

Fireflies are gradually disappearing from those areas most grievously impacted by urbanization. And along with the fireflies that we may notice dwindling, thousands of other species of insects are disappearing before we even know very much at all about their behavior or marvelous being.

Having long enjoyed exploring minute creatures with the aid of a traditional microscope, and being a long time fan of fireflies, I have long been curious to know what might be revealed should one take a closer look at fireflies using the aid of a scanning electron microscope. I was afforded this opportunity when approached by an associate to provide some firefly specimens for examination in preparation of a children's book. Thus through a collaborative effort I provided specimens and made suggestions of what to examine. The spectacular and amazing images below were made by Dennis Kunkel of Dennis Kunkel Microscopy, Inc. The specimens were collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Compound Eye of the Firefly, Photinus sp. Shown here is a SEM of the large spherical compound eye of Photinus sp. (Dwarf tribe of P. pyralis, Mt. Cheaha, AL). This image has been digitally enhanced to express the numerous hexagonal cuticular cornea or facets. Fireflies have two large compound eyes which have a dark black, shiny hue and coloration when observed by the naked eye. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Head of Photuris sp. Note the hard trilobel labrum between the mandibles which has three sawtooth-like, thorny projections which may act like a saw to aid in the cutting and ripping of flesh as Photuris devours other fireflies it preys upon. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

A closer view at higher magnification of the mouthparts of Photuris sp. showing clearly its grooved mandibles which inject its firefly prey with liquefying digestive fluid and the trilobel labrum used to saw and cut the flesh of those fireflies Photuris preys upon like a mythical vampire. Only in this case Photuris is a genuine vampire among the firefly world. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

This image of Photuris has been digitally enhanced to bring out the debris upon its grooved mandibles and surrounding mouthparts. Photuris females prey and feed upon Photinus fireflies and in the process acquire the milky white viscous and unpalatable blood of Photinus. This blood contains lucibufagins, distasteful pyrons which may provide Photuris with an advantage in its competition to survive that it lacks prior to ingesting the blood of Photinus. In this sense the voracious Photuris is the vampire among fireflies, that stalks its prey and lust for the pure, white blood of its relative gentle, angelic, virgin victims. The white, sticky blood of Photinus may be a contributing factor as to why highly magnified SEM images of both Photinus and Photuris which has fed upon Photinus have so much debris clinging to their body hairs and mouthparts. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Head of Photinus showing two large compound eyes, mandibles and mouthparts. Photinus is a rather gentle firefly compared to Photuris and lacks the promontory sawtooth structure between its mandibles. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

To understand what one sees in such highly magnified images it is necessary to have studied and observed living fireflies, especially in their natural environment. If one is not aware of the predacious behavior of Photuris upon Photinus, nor of the nature of the milky white viscous blood which flows through the veins of Photinus and is exuded from its pores, a proper interpretation of images is hampered. In the education of our children and students it is best to avoid such misinterpretation which is why I have endeavored to provide my own insight as to what these spectacular SEM images reveal. Note, for example the veracious nature of Photuris feasting upon Photinus in the video below. Then perhaps you can begin to understand the implications revealed in a closer, highly magnified view of the assailant's and the victim's morphology.

In addition to the predatory-prey relationship which exists between Photuris and Photinus fireflies, it is also necessary to understand that both species have developed adaptations which contribute to their survival as it relates to being active at night, flying about in search of a mate, or in the case of Photuris, in search also of prey. It is thus a critical factor that fireflies be able to cling readily to smooth, slick surfaced upon which they are often observed, as in perching, or upon which they may alight during their flight when a mate or prey is detected. This has resulted in the evolution of tarsal claws and pads that permit fireflies to cling to and walk over a surface as slick as glass, much as may a common house fly.

PHOTO Photuris sp. clinging upside down to lid of glass Petri dish. Fireflies are very agile creatures and can easily walk upon a slippery glass surface as demonstrated here by Photuris which is clinging to the glass lid of a Petri dish. This particular firefly had no difficulty walking upside down upon the glass lid of the Petri dish. Notice also that this species of Photuris has two hooked tarsal claws on each leg. These hooked claws are not only useful for grabbing and holding upon vegetation, but they enable Photuris to grapple males of Photinus which are lured by mimicking the flash response of female Photinus. Photuris is the raptor of fireflies, the great deceiver, the seductress which lures male Photinus, pouncing upon them, grabbing them with their hooked clawed tarsi, biting off their heads, then devouring them. After the feast a female Photuris may spend a number of days laying eggs in moist soil to begin a new generation of predacious fireflies.

The photograph above shows Photuris clinging upside down to the glass lid of a Petri dish. This firefly was able to easily walk upon glass upside down bearing its entire weight without difficulty or slipping. How is this feat enabled? The answer is revealed in the SEM images below which show that the tarsal claws and pads which are covered with a myriad of tenent setae.

This image shows the tarsal claw and pads upon the legs of Photinus sp. (Dwarf tribe of P. pyralis, Mt. Cheaha, AL). Note the forest of hairs or tenent setae which enable the firefly to easily cling to the smooth surfaces of leaves, grass, and other vegetation -- even glass. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

A firefly can also easily walk up the side of a glass jar or even hang upside down from the glass lid of a Petri dish walking across such smooth surfaces without falling. This is enabled by the many flat headed, fan-shaped tipped hairs which act to form a tarsal pad. Photinus fireflies also have a thick, milky white blood which may help moisten these hairs and provide adhesive forces enabling fireflies to walk over slick surfaces. Their grappling hook-like tarsal claws aid in clinging to vegetation, their mates, as well as in escaping from pupae.

The design and function of such tarsal pads as relates to secretion of an adhesive substance has been described by Stanislav. N. Gorb for the fly:

Flies (Brachycera) have adhesive pads called pulvilli at the terminal tarsomere. The pulvilli are covered by tenent setae, sometimes termed tenent hairs, which serve to increase the actual area of attachment to the surface. By using transmission and scanning electron microscopy it is shown that proximal and distal tenent setae have different ultrastructures. The design of distal adhesive setae is adapted for the release of adhesive substances close to the area of contact. It is concluded that secretion injection is precisely targeted under the distal tip of a single seta. (Source: S N. Gorb of the Max Planck Institute for Metals Research in Stuttgart, Germany)

Shoe fly: To walk on walls and ceilings, your feet have to stick, but they have to get unstuck, too Adams Summers describes how adhesive tenent setae enable flies to walk on walls and hows Gorb is endeavoring to patent the process in order to make gear which humans may use to scurry up walls, which may perhaps one day be used by rock climbers in pursuit of their sport. Gorb's work owes much to the earlier EM studies made by Bauchhennss in 1979 which revealed the structure of tenent setae on the pulvilli (adhesive pads) of Celliphorea flies and the fact that non-volatile lipid secretions were produced in Celliphorea flies to enable them to cling to and walk upon smooth surfaces. The follow-up research by S. N. Gorb did much to describe the mechanism by which tenent setae function in conjunction with the secretion of adhesive lipids. See figure below:

Tenent setae of syrphid fly Episyrphus balteatus illustrating the structure and mechanism of lipid-containing secretion. S.N. Gorb (2001) Attachment Devices of Insect Cuticle. (Source: Biomimetics: biological inspired technologies)

A closer view at higher magnification of the tarsal hairs (tenent setae) of Photinus sp. (Dwarf tribe of P. pyralis, Mt. Cheaha, AL). Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Yet another closer view at higher magnification of the tarsal hairs (tenent setae) of Photinus sp. (Dwarf tribe of P. pyralis, Mt. Cheaha, AL). Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

The tenent setae on tarsal pads of a firefly somewhat resemble those of an ordinary fly or horse fly. See more amazing SEM images of other insects at Duke University SEM Gallery

Photinus sp. Tenent Setae. The above photo has been digitally enhanced giving a golden hue to the forest of tarsal pad hairs. Also the image was digitally enhanced to repair damage to several tenent setae to produce a more ethically pleasing rendering. Note the tenent seta in the lower right which shows clearly that channels which carry lipid adhesives end in the spatulate pad; small globular debris may be solidified or coagulated lipid adhesives. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, and digitally enhanced by Terry Lynch.

The huge spherical eyes of Photinus sp. enable its twilight flights in search of a mate. Also note this image shows the two sickle-like, sharp pointed mandibles. In the larvae form the grooved mandibles act like a syringe and enables larvae to inject a strong, paralyzing digestive venom into soft bodied prey like earthworms. Note: This is a dwarf tribe of P. pyralis which was collected from atop Mt. Cheaha, Alabama, during the summer of 2004. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Yet another view of the tarsal claw of Photinus sp. and the forest of flat tipped hairs which form a clinging pad which enables these fireflies to walk over smooth surfaces of leaves and other vegetation -- even glass. Note: This is a dwarf species of P. pyralis collected atop Mt. Cheaha, Alabama, summer of 2004. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

The combination of a grappling hook-like claw and sticky foot pads enable fireflies to cling to smooth surfaces easily and should they encounter an obstacle in their evening flights they can grab onto it and avoid falling to the ground. Of course this equipment may also aid Photuris, a predacious species, to capture other fireflies luring male Photinus to their death, mimicking the flash response of a female Photinus, pouncing upon the unsuspecting males, grabbing them with tarsal clawed feet which grasp their prey and hold them tight with the aid of pads covered with thousands of sticky tenent setae. Certainly the ability to cling to smooth surfaces and scamper across them rapidly would also aid Photinus fireflies in escaping an enemy or predator.

In the case of Photuris their tarsal claws are used to aid in ripping apart Photinus fireflies upon which they prey; plus, the trilobel labrum aid Photuris in tearing apart the flesh of prey. Photuris is even able to make aerial assaults and capture other fireflies in flight, its powerful tarsal claws and adhesive tarsal pads clinging to prey while Photuris rips into the delicate flesh beneath their pronotum to cut through nerves and paralyze its victims.

These images illustrates the spectacular complexity and hidden wonders of such common insects as the firefly. Known for its romance inspiring twilight dances flying over field, meadow and forest, who would have ever expected that the feet of a firefly are also carpeted in a magnificent garden of fan tipped, sticky tarsal hairs which aid predacious fireflies in capturing their prey!

Tarsal claw of Photinus sp. (Dwarf tribe of P. pyralis from Mt. Cheaha, AL) digitally enhanced to add a golden sunset hue. Copyright © 2011 by Dennis Kunkel Microscopy, Inc. Specimen collected, preserved, provided, identified, described, and digitally enhanced by Terry Lynch.

Yet also revealed when one looks closely at the firefly, its behavior and its morphology, is that fireflies are highly adapted to survival and are engaged in what is nothing less that firefly warfare! Each species of firefly is competing for territory and armed to the teeth, of should I say, mandibles, with an assortment of weapons.

Adult fireflies use their flashing lanterns to signal and compete for a mate; this also enable the establishment of social networks of fireflies of the same species or tribe. In the case of Photuris, they use their tarsal claws and amazing sticky padded feet to capture prey which are lured to their death by flash patterns that mimic that of a female Photinus. Photinus fireflies represent an enemy to Photuris that is in competition for territory, and territory means food for a new generation of firefly larvae. The large, robust adult female Photuris lure Photinus to their death, pouncing upon them grabbing them with their tarsal clawed, sticky feet, holding them fast, then biting them with their sickle-like grooved mandible. Once the Photinus male is overpowered and subdued, Photuris uses its mandibles and trilobel sawtooth-like labrum to rip apart their prey which they inject with a highly corrosive digestive venom; then they devour their prey alive.

Firefly larvae express this same behavior in eating soft bodies animals such as earthworms and snails. Hence fireflies are not so much engaged in romance as they are in a fierce competition and warfare, using species specific coded flashes of light as a form of communication to not only find their mate, but to establish social networks that act as armies and tribes seeking to rule and dominate the fields, meadows and forest which they grace with their evening flashing flights.

As a child one might marvel at fireflies sparkling upon a summer's eve, capturing them in a jar and watching curiously, wondering how they make their light. But upon closer examinations and inquiry one is made aware that all is not what it seems. Fireflies are a waring species and their entire evolution has been geared toward creating an insect that is an organism designed to dominate territory which is a food source for its larvae young. Then as adults fireflies use their coded flashes to find a mate or, in the case of Photuris, to find their prey, which they feast upon after savagely luring them into their tarsal claws and voracious mandibles.