Flameless Fireflies

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Fireflies (family Lampyridae, order Coleoptera) are drifting over fields and landscapes in Ohio. Numbers tend to climb through June peaking in July.


There are 67 genera and over 2,000 species of fireflies worldwide and about 170 species are found in North America with most occurring east of the Mississippi.  Ohio is home to around 25 species. 




The beetles are referred to by many common names including “fireflies,” “lightningbugs,” and “lightning beetles.”  All are based on the ability of adults and larvae to emit dazzling bioluminescent light. Even the family name, Lampyridae, is a glowing reference to the beetle’s luminosity.


It’s a marvel of nature that the fireflies produce light without heat. The complex cascading chemical reactions inside the beetle’s light-producing organ, called a “lantern,” are 100% efficient. No energy is lost to heat. Otherwise, the name “fireflies” would have an entirely different meaning.




However, there are beetles in the Lampyridae family that do not produce light. Unlike their crepuscular or nocturnal flashing cousins, these non-luminescent lampyrids are active during the day. They are commonly called “diurnal fireflies,” but a more accurate name would be “diurnal flameless fireflies.”


Diurnal Firefly


They also overwinter as adults while the flashers spend the winter in the larval stage. Thus, diurnal flameless fireflies are sometimes called “winter fireflies” owing to the ability of the adults to survive low winter temperatures.


Diurnal Firefly


I came across these unusual lampyrids in a park in southwest Ohio while searching for Emerald Ash Borer (EAB) (Agrilus planipennis) adults. An effective technique for searching for the little green monsters is to stand beneath an ash tree and look up through the foliage. EAB adults commonly rest on the upper leaflet surface, and you can spot them using the “skylight” effect.


I spotted beetles that were about the same size and shape as EAB resting on the lower leaflet surface. A closer look revealed the dark-colored beetles had distinct firefly markings on their prothoracic shield, which is the flat structure covering the head. However, they had no lanterns on the underside of their tale ends.



Diurnal Firefly


Diurnal Firefly


Diurnal Firefly


Apparently, it is common to find these interesting lampyrids on trees; it’s one of their favorite hangouts.  The beetles feed on pollen and nectar, so trees located near naturalized areas are also favored.


Diurnal Firefly


At one time, it was speculated that these flameless fireflies are primitive lampyrids. They represent the way fireflies once looked and behaved before they embarked on their evolutionary Quest for Fire. However, research on the phylogenetic relationships of fireflies has revealed that the story behind flameless fireflies is far more complicated. I’ve included some of the key scientific papers under “Selected References” below.


One thing that’s retained by non-luminescent diurnal fireflies is bioluminescent larvae. Thus, it’s accurate to call their larvae “glow-worms,” just like other fireflies. They also share the same carnivorous lifestyle with other fireflies by grabbing meals consisting of slugs, snails, and the larvae of other insects. In fact, they are considered important beneficial insects.




On the other hand, it’s believed that the luminosity of glow-worms keeps them from becoming meat meals themselves. The glow is a warning (aposematic) display signaling to would-be predators that eating the larvae could be their last meal.




It's a serious warning. Both the larvae and adults of all fireflies have defensive steroidal pyrones known as lucibufagins. The “-bufagins” suffix references the well-studied bufadienolide toxins found in toads belonging to the genus Bufo.


A report on firefly toxicosis published in 2008 describes how two Bearded Dragon lizards (Pogona vitticeps) were accidentally killed as a result of being fed fireflies belonging to the genus Photinus which are native to the eastern U.S. The lizards are native to Australia, so it’s speculated they never evolved self-protective avoidance behaviors. Both lizards died within 90 minutes of eating the fireflies.


It’s hypothesized that firefly larval aposematic bioluminescence is the first function and earliest origin of bioluminescence in Lampyridae. Subsequently, adults gained the ability from their larvae to flash sexual signals to find a mate. Of course, signal patterns for different firefly species have been well studied and documented.


So, how do the diurnal flameless fireflies find mates? They kept the ability shared with some flashers to use pheromones wafting from the waxy film on their backs to send “come-hither” signals to a mate.


Diurnal Firefly


Finally, why did the flameless fireflies lose the ability to flash? Bioluminescence isn’t just used by fireflies to attract mates. Fraudulent flickering is used to arrange dinner dates.  Females of the genus Photuris can mimic the flashing patterns of females in the genus Photinus to attract and eat Photinus males. The deceptive behavior has earned the females the moniker “femme fatale fireflies.”


Authors of a paper published in 2006 provide evidence that diurnal non-luminescent fireflies switched to daylight hours to avoid predation by the femmes fatales giving new meaning to daylight saving time. Of course, the diurnal fireflies lost their fire because they no longer needed to produce light to attract their flame.



Selected References (Listed by the Date Published)

Branham, M.A. and Wenzel, J.W., 2003. The origin of photic behavior and the evolution of sexual communication in fireflies (Coleoptera: Lampyridae). Cladistics19(1), pp.1-22.


Fitzgerald, K.T. and Newquist, K.L., 2008. Poisonings in Reptiles. Veterinary Clinics of North America: Exotic Animal Practice. 11(2), pp.327-357. ISSN 1094-9194,


Gronquist, M., Schroeder, F.C., Ghiradella, H., Hill, D., McCoy, E.M., Meinwald, J. and Eisner, T., 2006. Shunning the night to elude the hunter: diurnal fireflies and the “femmes fatales”. Chemoecology16, pp.39-43.


Stanger-Hall, K.F., Lloyd, J.E. and Hillis, D.M., 2007. Phylogeny of North American fireflies (Coleoptera: Lampyridae): implications for the evolution of light signals. Molecular phylogenetics and evolution45(1), pp.33-49.


Oba, Y., Furuhashi, M. and Inouye, S., 2010. Identification of a functional luciferase gene in the nonluminous diurnal firefly, Lucidina biplagiata. Insect molecular biology19(6), pp.737-743.


Ming, Q.L. and Lewis, S.M., 2010. Mate recognition and sex differences in cuticular hydrocarbons of the diurnal firefly Ellychnia corrusca (Coleoptera: Lampyridae). Annals of the Entomological Society of America103(1), pp.128-133.


Martin, G.J., Branham, M.A., Whiting, M.F. and Bybee, S.M., 2017. Total evidence phylogeny and the evolution of adult bioluminescence in fireflies (Coleoptera: Lampyridae). Molecular phylogenetics and evolution107, pp.564-575.


Oba, Y., Konishi, K., Yano, D., Shibata, H., Kato, D. and Shirai, T., 2020. Resurrecting the ancient glow of the fireflies. Science advances6(49), p.eabc5705.


Lower, S.E., Pask, G.M., Arriola, K., Halloran, S., Holmes, H., Halley, D.C., Zheng, Y., Collins, D.B. and Millar, J.G., 2023. Identification of a Female-Produced Sex Attractant Pheromone of the Winter Firefly, Photinus corruscus Linnaeus (Coleoptera: Lampyridae). Journal of chemical ecology49(3), pp.164-178.


Novák, M. and Jakubec, P., 2024. Beyond the glow: proving the unity of pheromones and bioluminescent signals in glow-worm firefly courtship. Zoological Journal of the Linnean Society, p.zlae045.