It’s moth watching time and bugs of all sorts arrive from the darkness to whirl and whiz around the black light in my backyard. Something lands on my hand and I shake it off without much notice. It’s not unusual to have a variety of insects landing on me when I’m near the light. On the ground below me in the beam of my headlamp lies a small Burying Beetle that was just tossed from my hand. These beetles are true to their name. They bury carcasses of small animals as a food source for their larvae. This beetle had left a rather pungent and peculiar smell on my hand.
With nearly 70 species worldwide and only about 8 species here in New England, these red and black beetles are unmistakable. My beetle turned out to be a Burying Beetle or Roundneck Sexton Beetle (Nicrophorus orbicollis), apparently one of the most common species in this area. Lots of them are colored red and black, but only this one has a round pronotum, the plate of armor between its head and abdomen.
My hand didn’t smell gruesome at all. It was a sweet smell that resembled horse manure, but much more pungent. I actually kind of liked the smell. But what exactly caused it? Was it residue on the beetle from rotting flesh? Was it emitting a chemical of some sort? Either way, I first went inside and washed my hands before exploring for an answer. My mother would be proud.
Carrion beetles are chemical wizards. Using their clubbed antennae, each with three orange segments on the end, males can detect a dead carcass over a mile away. When a carcass is secured he emits a pheromone to attract a female. Perhaps my hand was sprayed with his pheromone?
I once had an instructor for a hazardous materials course for my firefighting certificate. He liked to call everything “methyl-ethyl bad stuff” with his tongue firmly in his cheek. It turns out that carrion beetles actually make it. A close relative of this beetle emits a pheromone comprised of ethyl 4-methyl heptanoate, which apparently has a strong fruity smell. Not a very good descriptor of the smell on my hand.
Once the male secures the carcass and attracts a female, both bury the carcass. They produce oral and anal secretions that help reduce decay by inhibiting bacteria. The female lays eggs in the soil near the carcass rather than right on it. They are unusual among insects in that both the male and female parents tend to the brood. The adults eat the carrion and regurgitate the food for the larva. After about a week the parents leave the brood and the larvae pupate in the soil.
Whether from the residue of a rotting carcass, mate attracting pheromones, or anal secretions able to stave off bacteria, the burying beetle left me with more than a smelly hand. He left me with yet more wonder for the ecological workings of my backyard.