Geotrupid

I was walking up the path under the black walnut trees in my parents’ yard this afternoon when I spotted a minor commotion at ankle level: a bald-faced hornet and a large, metallic-green beetle seemed to be arguing over something, though the hornet flew away when I bent down for a closer look. The beetle was right in the middle of the path, about a foot away from a file of fairly fresh cat shit, so I figured it was some sort of dung or scarab beetle. Anxious for a good photo, and mindful of my brother Steve’s interest in documenting all the beetles on the mountain, I set down the bag of vegetables I was carrying and scooped up the beetle.

In contrast to yesterday’s frog, the beetle fought hard to escape, wedging its head and forelegs into a crack between my fingers and pushing with immense force. I barely managed to hold it in. I ducked inside just long enough to grab the camera, and set the beetle down on the concrete walk, where I’m sorry to say it rolled onto its back and I shot a few photos of it in that compromising position before helping it right itself. The feather-like protrusions on the ends of its antennae — evidently called antennomeres — glowed orange in the late afternoon sun as it turned and began marching purposefully toward the tall grass. I stuck out a hand and herded it back into the sunlight, whereupon it stubbonly began heading back in the same direction. The second time I stopped it, it emitted a loud chirping sound — if I’d ever wondered what a pissed-off dung beetle sounded like, this was my answer. Then it lifted its elytra, unfolded the sails of its underwings, and took off, buzzing at least as loudly as a June beetle.

I emailed Steve for an I.D., and he responded quickly.

I don’t suppose you thought to collect it?! That’s a pretty rare beetle, Geotrupes balyi (species 90% certain, genus certain). It used to be considered a scarab, subfamilae geotrupinae, but now it’s in a separate family, Geotrupidae, the “earth-boring dung beetles.” The geotrupids look a lot like tumblebugs and other scarabaeid dung beetles; they roll balls of dung, etc. However, they generally live underground and are seldom collected in the USA. They are much more common in Europe; Fabre has a segment on dung beetles which are geotrupids. The well-known “spring dor beetle” of Europe (also just called a “dor,” a good scrabble word) is a bluish geotrupid quite common in much of the European continent. I’ve never collected or seen a geotrupid on the mountain before, so this is a new species and family for bioplum [our family’s biological inventory of the property].

The invaluable BugGuide.net includes some photos of this species, and I can see why Steve considers it the most likely candidate. The contributor, a fellow named Jim McClarin who is obviously at least as big a beetle fanatic as Steve, says, “I found this fellow in/on a mushy, slimy, rotting mushroom near a small pond or seasonal pool in mixed woods” in Rockingham County, New Hampshire. He offers “Mushroom geotrupid” for a common name.

So is this beetle coprophagous (dung eating) or mycetophagous (mushroom eating)? The authoritative Generic Guide to New World Scarab Beetles (which defines “scarab” broadly) says that Geotrupidae may be either.

Life histories of the geotrupids are diverse, and food habits vary from saprophagous to coprophagous and mycetophagous, and some adults apparently do not feed. Adults of most species are secretive, living most of their life in burrows. Although adults do not tend larvae, adults provision food for larvae in brood burrows. There is overlapping of generations in some species. For example, in the genus Bolboceras, eggs, larvae, pupae, and adults have been observed together in a single branching burrow. Adults dig vertical burrows (15-200 cm in depth) and provision larval cells with dead leaves, cow dung, horse dung, or humus. Burrows of some species extend to a depth of 3.0 meters. In restricted habitats, some species are semi-colonial. Geotrupids are not of economic importance, although their burrowing has occasionally caused damage in lawns. Adults of many geotrupids are nocturnal and are frequently attracted to lights at night. Some species are attracted to fermenting malt and molasses baits. Most adults and larvae stridulate. The biology and behavior of many species, especially the Bolboceratinae, are poorly known.

I can vouch for the stridulation. And it sounds like if I want to attract more of them, I need to get my ass in gear and ferment some malt. After all, who needs dung or rotting mushrooms when there’s beer?