ARTHROPOD MUSEUM NOTES

Number 93 • January 11, 2012 • Jeffrey K. Barnes

American burying beetle
Order: Coleoptera
Family: Silphidae
Genus and species: Nicrophorus americanus Olivier

confused flour beetleAmerican burying beetle

The American burying beetle is a member of the carrion beetle family Silphidae. It is large, with some individuals reaching a length of 1.5 inches. It is similar to other species of Nicrophorus in that it is shiny black and distinctively marked with two bright organ bands on each wing cover, but unlike the other species its pronotum and frons are also bright orange.

In the past, the American burying beetle was widely distributed in southeastern Canada and 35 states in the eastern and central United States. Population decline was well underway east of the Appalachian Mountains by the 1920s, moving from north to south. Decline in the Midwest proceeded from the center of the range outward, and all specimens collected since 1960 have been found on the periphery of the range. Today, the American burying beetle is known primarily from three areas in the eastern United States. A well studied population occurs on Block Island, off the coast of Rhode Island.  An extensive metapopulation occurs in central and southern Nebraska, and another metapopulation occurs in eastern Oklahoma and west-central Arkansas. Populations also have been found in South Dakota and southeastern Kansas. It was previously thought that the beetles were strictly associated with eastern deciduous forests, but it is now known that carrion availability is a more important factor in beetle distribution than is habitat.  Beetles have been found in grassland prairie, along forest edges, and in scrubland.  The American burying beetle  was officially listed as a nationally endangered species in 1989, but it had been cited as endangered by the International Union for the Conservation of Nature in the Invertebrate Red Book as early as 1983.  It is generally believed that the species’ decline has been caused by changes in habitat and carrion food resources.

The nocturnal adult beetles are remarkably adept at finding recently dead vertebrates. Both parents prepare the carrion and care for the young. After locating the carcass, they move underneath it, flip themselves onto their backs, and test their ability to lift the dead animal. If the substrate is the proper consistency for burial, the beetles gradually move the soil underneath the carcass to the side, and the carcass settles into the ground and is covered with more soil. Nighttime burial must be accomplished swiftly in order to deny access to other carrion consumers, such as carrion flies that lay eggs during the daytime. The beetles then remove hair or feathers and shape the carrion into a compact ball and add secretions that preserve the carrion and alter the course of decomposition. The female lays 10–30 eggs in a short chamber above the carrion. Both parents regurgitate droplets of partly digested food into a conical depression on top of the carcass prepared by the female. This serves as nutrition for newly hatched larvae. The larvae are soon able to feed themselves as they grow rapidly. The parents provide care for the duration of larval life, removing fungi from the carcass and covering it with an antibacterial secretion. If too many larvae are growing on a carcass of limited size, the parents cannibalize the smaller individuals. The living larvae mature and pupate in nearby soil in about a week, and new adults emerge about a month later. Adults live for only one season.