Cobweb Beetle

The cobweb beetle (Ctesias serra) is a small dermestid beetle in the family Dermestidae, notable for its association with dry organic debris including the detritus found in spider webs—an ecological niche reflected in its evocative common name. Measuring just 2–4 millimeters in length, this inconspicuous insect is covered in a pattern of pale and dark scale-like hairs that provide camouflage among the fibrous materials it inhabits. The cobweb beetle's larvae feed on accumulated dry organic matter such as shed arthropod exoskeletons, dead insects trapped in cobwebs, hair, feathers, and similar keratin-rich materials, making this species a minor participant in decomposition cycles in sheltered microhabitats. Adults are found in similar environments, typically within buildings, under bark, in bird nests, and in the accumulated debris beneath spiders' webs in caves and outbuildings. The species is distributed across much of temperate Europe, ranging from the British Isles through Scandinavia and central Europe, with records from Belgium, Denmark, Sweden, Switzerland, and neighboring countries. Ctesias serra is the sole member of its genus in Europe, though related species occur in other regions. Like other dermestids, it can occasionally become a minor pest in natural history collections, wool products, and dried food stores. The species is classified as Least Concern given its widespread distribution and ability to exploit diverse sheltered microhabitats.