Background Biology of Carrion Beetles
When a terrestrial vertebrate dies, a fierce competition begins for the nutrients stored in its decomposing carcass. The competitors that use carrion as food (for themselves and their young) include vertebrate scavengers; invertebrates, such as ants, flies, and beetles; soil dwelling fungi; and bacteria. These various organisms locate the carcass by honing in on odors released as the carcass decays. Among the most unique and sensitive of these organisms are the carrion beetles (Order Coleoptera, Family Silphidae). Carrion beetles can find carrion within an hour of death and from up to 1.5 miles (4 kilometers) away by using olfactory organs located on their antennae. In addition to their remarkable ability to detect the odor of death, carrion beetles generate interest because they are large and brightly colored. In fact, beetles in the genera Nicrophorus and Necrodes often comprise the largest beetles in student insect collections.
Although they occur worldwide, carrion beetles are a relatively small family of insects with only 208 described species in 13 genera. In North America, there are eight genera (six of which occur in Nebraska) and 30 species (18 are in Nebraska). Among their ranks is a group that has the unique feature of carcass burial and includes a federally listed endangered species. Although few in number, the carrion beetles of North America are found in most terrestrial habitats and multiple species often occur together. These factors have made them some of the most intensely researched insects in North America.
The family Silphidae is divided into two distinct subfamilies, based on beetle morphology and behavior. Members of the subfamily Silphinae arrive during the early to middle stages of carcass decomposition and lay eggs on or near the carcass. Their young then feed on the fly larvae that are present on the carcass. As a result, these insects provide a valuable ecological service by reducing the number of flies and the potential for disease transmission. Although they are diverse, their biology differs little from other insects and thus, as a group, they have received relatively little research interest.
Unlike the Silphinae, carrion beetles in the subfamilyNicrophorinae display the unique behavior of burying and tending carcasses, earning them the common name of "burying beetles". Upon carcass discovery, burying beetles crawl under the carcass and assess its mass. If the carcass is appropriately sized, a male and female pair entombs the carcass. The burial process is thought to reduce the chances of discovery of the remains by other decomposers, including flies that could displace the beetles from the carcass. Breeding pairs of burying beetles work together to acquire and prepare the carcass as a reproductive resource. The bi-parental care of the resulting brood ball and offspring is a feature unique among insects. One of the species in this subfamily is the American burying beetle, Nicrophorus americanus, the only federally endangered insect in Nebraska.
This web site was developed to increase public awareness of the importance of carrion beetles in the environment and to serve as a resource for the study of this interesting group of insects. The site includes pictures, video clips, distribution maps, ecological information and identification tips for all of Nebraska’s carrion beetle species. Dig in!