Nature’s notebook

When yucky work is required, these beetles step up

Carrion beetle on a pawpaw fruit. Photo: Fritz Flohr Reynolds, via Flickr (CC BY-SA 2.0)

Maybe it was the ghoulish nature of Halloween – or the ghastly rhetoric of the recent election – but I’ve found myself thinking about the carrion beetles (Necrophilia americana) I encountered last spring.  They were in a path between a stand of trees along the Uwharrie River and a field of native warm season grass. Their distinctive shape and coloration caught my eye. Carrion beetles are flat – a little larger than my thumbnail – with shiny black wings folded over their back. The dark splotch in the center of their gold pronotum makes them look as if their shoulders have been inked with a prominent tattoo.

Their frenetic activity made it difficult to get an accurate count, but there must have been at least a dozen.  On closer inspection, I noticed they were emanating from the body of what was once a large rat.  It had already been stripped of its fur. They were as industrious as ants or honeybees. I figured if you made your living on a rotting carcass, then time was of the essence. As I drew closer with my camera, they abandoned the corpse and scurried off into the grass. Being accustomed to immobile prey, they probably found the slightest motion extremely disconcerting.

When an animal dies, bacteria in the gut produce odorous gasses, quickly attracting flies in search of a place to lay their eggs. Within hours, the first maggots have hatched. The carrion beetles aren’t far behind. They feed on the carcass itself, but also on the maggots, their rivals for this sustenance.  According to Piedmont naturalist extraordinaire Bill Hilton Jr., phoretic mites sometimes hitch a ride on the back of a carrion beetle. This is a classic example of a symbiotic relationship. The beetle transports the non-flying mite to its food source, and the mite consumes fly eggs and maggots, helping the beetle keep their population in check.

After a female carrion beetle mates and lays her eggs, she flies away – taking some of her friends, the maggot-eating mites – in search of another freshly dead animal. She has to leave enough of the carcass for her progeny to eat when they hatch in roughly a week. When the larvae mature, they drop to the ground, then bury themselves to pupate. They overwinter as adults. Carrion beetles generally prefer moist habitats, and they are most often spotted during warm weather. (With the multitudes of deer carcasses left by cars and unscrupulous hunters this time of year, it’s a pity they aren’t more active in winter.)

In researching this article, I noticed some of the information about carrion beetles was posted by exterminators. I was shocked that anyone might consider these creatures a pest. They help humans in all sorts of ways. They can aid police investigations, assisting forensic entomologists brought in to determine the time of death. Without them, the state of our landscapes – especially our roadsides – would be atrocious. And they do this unsavory work completely free of charge. Along with maggots, vultures and other scavengers, carrion beetles provide an invaluable public service. If only we could get them to clean up our political system. 

For more information on carrion beetles, see the entries at This Week at Hilton Pond and The Hiker’s Notebook.