This small member of the Pyrochroidae or Fire-colored Beetle family is reliably out and about in early May at Mount Pisgah. In addition to the flashy name, this beetle likes to play with fire as well.
Male Fire-colored Beetles (FCB’s) such as this Pedilus inconspicuus have a crazy relationship with Blister Beetles, which are much larger, beefy beetles known for their bodily blistering compound. The toxin keeps them from being lunch for other animals, and the FCBs find it useful for themselves as well. FCBs use the chemical, cantharidin, to lure females, which then use the substance to protect their eggs.
How do the Fire-colored Beetles acquire cantharidin? There are a few strategies: Climb on the back of a Blister Beetle and basically lap the substance from it. Munch on the bigger beetle’s wings. Or, pester the beetle’s leg: Blister beetles do a thing called “reflex bleeding” where they release the poisonous liquid from glands on their legs when they’re disturbed.
Pedilus inconspicuus lives only in Oregon and California, but there are other members of the genus that also live here. Perhaps the others are more extroverted? This one’s species name seems to suggest that it’s secretive.
As a matter of fact, there are several beetles out there wearing the same costume as this one, with red behind the head and black-to-coppery wings. Note that Pedilus beetles have heads and thoraxes measuring less wide than their abdomen, and have a narrow “neck” area behind the head.
Stay curious!
P.S. Don’t forget to check out Karen’s 2025 blog, The Daily Insect. Many of the featured creatures were photographed at Mount Pisgah.
Sources:
A photo of an oil beetle with two Pedilus genus beetles riding on it: https://bugguide.net/node/view/910456. Accessed 4/30/25.
The Bug Lady’s page on Fire-colored Beetles: https://uwm.edu/field-station/bug-of-the-week/fire-colored-beetle/. Accessed 4/30/25.
All photos by Karen Richards.