what is this bug
Location: Southwest Virginia
October 27, 2011 3:50 pm
Every fall I see these things in my backyard. They gather together on a certain plant and I guess they eat it. Anyway it always dies where they were.
These are Oil Beetles, a group of Blister Beetles in the genus Meloe. There are 12 similar looking species on BugGuide, and we don’t have the necessary skills to differentiate your species from the others. Because of your location and the time of year, we believe the most likely species candidates based on data information on BugGuide are Meloe campanicollis and Meloe impressus. Oil Beetles have an interesting and complex life cycle that includes laying eggs that hatch into mobile larvae that attach themselves to solitary bees. When the bee returns to the hive, the beetle enters with the bee and begins by feeding upon the egg of a bee as well as the food that has been provided to nourish the bee larva. Here is the explanation on BugGuide: “First-instar larvae climb to the top of a grass or weed stalk as a group, clump together in the shape of a female solitary ground bee, exude a scent that is the same as, or closely resembles, the pheromones of the female bee, and wait for a male ground bee to come along. When he does, he tries to mate with the clump of larvae, whereupon they individually clamp onto his hairs. He then flies away, finds and mates with one or several real female bees, and the larvae transfer to the female(s). Each impregnated female bee then flies off and builds one to several nests in burrows she digs in the soil, and the larvae transfer again to the new nests. The female bee stocks these nests with honey and pollen for her own young, but the hungry blister beetle young are there to gobble up the provisions. They eventually pupate and finally emerge as adult flightless beetles. Brothers and sisters find each other and mate, produce eggs and the hatchlings start the process all over.” BugGuide does not provide much information on the food plants for the various species. Have you been able to identify the plant that your beetles are feeding upon? Is it something that you cultivate in your garden or is it a native plant? The Backyard Arthropod Project has a nice set of photos and some interesting observations.