By Arthur V. Evans
Today was cool, gray, and blustery–not exactly what I would call ideal conditions for finding insects. Nevertheless, I set out for the woods along Jordans Branch in Bryan Park here in Richmond, Virginia in hopes of finding early spring species to photograph. I ambled down a trail through a stand of holly toward a mixed woodland of loblolly pine and various hardwoods. As I knelt down to inspect the trunk of a pine snag, a faintly beetlish outline partially hidden in a crack in the bark caught my eye.
It was a winter dark firefly, Ellychnia corrusca. Flat and soft-bodied, the beetle measured slightly more than one half inch in length. It remained motionless until I gently coaxed it out of its hiding spot with a pine needle for a better look.
Winter dark fireflies are mostly dull black, but the sides of their flattened, shield-like midsections are marked with yellow, orange, or reddish arched bands. Their soft, pliable wing covers are clothed in short, fine, golden hairs.
Mature larvae pupate in dead logs, especially pines. Adults emerge in late summer and fall and are sometimes encountered on trees or on the flowers of goldenrod and other asters. As temperatures begin to drop, they seek protected places under bark for the winter. The beetles reappear on late winter and early spring days, either resting on bark or circled around sap flows on maples like cattle around a trough.
Like their more familiar cousins of summer, winter black fireflies are bioluminescent, at least for a while. Both the larval and pupal stages produce their own light. Even freshly emerge adults maintain this youthful glow, but as the beetles grow older they lose their light-producing organs.
Mating winter dark fireflies are not an uncommon sight. Their courtship involves two stages. First, the male climbs on the back of the female while constantly touching her with his antennae and mouthparts. This activity alone may last for up to half an hour. Afterward, the couple consummates their relationship by joining their bodies as they face away from one other. Sometime during the next hour or so, the male transfers a protein-packed packet, or spermatophore, to the female. Pairs of beetles sometimes remain joined together this way for up to an entire day. Over the next several days the female will slowly digest the spermatophore inside her body and store it as a source of energy in her body. Both males and females will mate several times before dying in late spring or early summer.
When attacked, these beetles exude a bitter fluid from their leg joints. This defensive strategy, known as reflex bleeding, is also practiced by other species of lightningbugs.In spite of their chemical defenses, phorid flies attack winter dark fireflies and their kin. Just how the flies locate their hosts is unknown, but their maggots develop inside the beetle, killing their beetle host as they emerge to pupate.
Recent studies suggest that winter dark fireflies are not a single species, but represent a complex of closely related, yet undescribed species that inhabit most of eastern North America. The taxonomy and natural history of these handsome, delicate, harbingers of spring would make an excellent study for a student looking to make a significant scientific contribution to the study of North American beetles.
© 2010, A.V. Evans