Ron Wilson

Ron Wilson

Want to know more about Ron Wilson? Get his official bio, social pages and more!Full Bio


Flameless Fireflies - Joe Boggs

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.”



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.



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.






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.



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 case study published in 2006 describes how zookeepers in the U.S. accidently killed two Bearded dragons (Pogona vitticeps) by feeding them 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.



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.


Sponsored Content

Sponsored Content