Establishing age-based color changes for the American Burying Beetle, Nicrophorus americanus (Olivier)

Abstract

The American Burying Beetle, Nicrophorus americanus (Olivier) is the largest North American species of carrion beetle (Silphidae). Due to prey loss and 90% reduction in historic range is federally listed as threatened at this time. Recovery of the species requires observation and cataloging of individuals captured in the wild. Research has been conducted to determine the lifespan, habitat, and range of the beetle; however, it is difficult to determine age in the field beyond teneral (young) and senescent (old). Since a demonstrable color difference was observed under laboratory conditions, we propose that a color gradient exists and can be used estimate the age of an individual beetle. From data of four beetles over their lifetime, the color of the pronotum and elytral markings were shown to darken in a gradual, predictable manner with ageing. The elytral markings darkened at a slower rate than the pronotum. Applications to field research are discussed as well as potential complicating variables including pigment involved, temperature, and other environmental factors.