One of the great stories of carabid beetles is their ability to produce, store and deliver defensive chemicals using their paired pygidial glands. Most people that know anything about this, know about the bombardier beetle and its awesome boiling hot discharge. But not as many people know that all members of the family Carabidae, and in fact beetles of all the families of the suborder Adephaga, have chemical producing glands in their abdomens. Most just have chemicals that smell bad and are irritating, only a few have the bombardier ability. One that isn’t explosive, but is notorious for its stench is Nomius pygmaeus. This one was dubbed “The stink beetle” in the Peterson beetle guide. The species is fairly rarely found. I’ve only collected two individuals on one occasion in the Rincon Mts. Using those specimens we did some preliminary chemical analysis of the wicked-stinky gland products, but didn’t have enough material to feel that we had conclusive results (anyway, preliminary results were way too weird to mention without confirmation).
The next best thing to The Stink Beetle is its relative, the much more common Psydrus piceus . These beetles are almost as stinky. Surprisingly, some claim they don’t smell bad, (see Wiki entry)
I am sure their nose must be broken or they have never sniffed one themselves. This species puts out a blend of aromatics and sulfur compounds. It doesn’t smell like anything you want to eat, nor will it be on the room air “freshener” market anytime soon. You can find them under bark of medium to large pine logs throughout their range in western North America and they are quite common in the Sierras of California. This is a picture of one taken during the mot recent Essig Museum field trip.
All carabids produce some sort of compounds, many with very recognizable odors. I guess the long-standing joke that it isn’t really stink, it’s the smell of success, has a bit of truth to it.