Chrysomya bezziana, also known as the Old World screwworm fly or screwworm, is an obligate parasite of mammals. Obligate parasitic flies require a host to complete their development. Named to honor the Italian entomologist Mario Bezzi, this fly is widely distributed in Asia, tropical Africa, India, and Papua New Guinea. The adult can be identified as metallic green or blue with a yellow face and the larvae are smooth, lacking any obvious body processes except on the last segment.

Chrysomya is an Old World blow fly genus of the family Calliphoridae. The genus Chrysomya contains a number of species including Chrysomya rufifacies and Chrysomya megacephala. The term “Old World blow fly” is a derivative of both the associated family, Calliphoridae, and the belief that the genus Chrysomya originated in Asia and migrated to North America only relatively recently. Chrysomya’s primary importance to the field of medico-criminal forensic entomology is due to the genus’ reliable life cycle, allowing investigators to accurately develop a postmortem interval. Chrysomya adults are typically metallic colored with thick setae on the meron and plumose arista. The name comes from the word chrysos, meaning “golden” in reference to the metallic sheen of the genus’ species, and -mya, a derivation from the word myia, meaning “fly”.