The Diurnal Firefly is one of my favorite finds at Mount Pisgah recently. These black insects with red “bracket” markings on their thoraxes are beetles, not flies. And because the fireflies we have in Oregon don’t light up, you could say they are neither fiery nor a fly. Still, there’s plenty about them to spark some interest.

Our Oregon beetles are in the same scientific family as eastern lightning bugs or fireflies (Lampyridae), but in the Ellychnia genus. Diurnal means daytime, and these beetles are active during the day, whereas the ones that luminesce reserve their energy for after sunset. They’re also known as winter fireflies because they spend the winter as adults, and are tolerant of the cold, unlike eastern fireflies that are active in mid summer, but spend winters as larvae. People see adult Ellychnia when it’s quite cold, sometimes just above the snow on tree trunks. I found a web post from the entomology duo The Bug Chicks from late November, 2014 when they saw one of these beetles at Mount Pisgah. There’s a link below.

The larvae live quietly in leaf litter and among tree roots, so they’re well hidden. As far as I can tell, it’s still unknown whether the larvae of any of these western beetles have light-producing organs. Some non-luminescent adults of east coast Ellychnia do have larvae with lanterns. Larvae that can light up are called glow worms. 

An interesting research paper I came across said that Lampyridae beetles that don’t glow have stronger pheromone detectors than those that light up. That’s because they can’t rely on photo-signaling to attract a mate, so their chemical signals need to be more effective. 

Stay curious!

Karen Richards


The Bug Chicks article. Accessed 10/4/20

Article by firefly researcher Sara Lewis that mentions Ellychnia corrusca light up as larvae. Accessed 10/4/20.