Cheese Flies

The species known as “cheese flies” are the best-known members of the family Piophilidae. This family of flies are scavengers of animal products, carrion, food products and fungi. They are sometimes useful in in forensic entomology and medical entomology.

The cheese fly, Piophila casei, is a small species, about four mm (1/6 inch) long. The fly’s larvae infest cured meats, smoked or salted fish, cheeses, and carrion. The mature larva is about 1/3 inch long and is sometimes called “the cheese skipper” because of its leaping ability – When disturbed, this tiny maggot can hop some six inches into the air. Adults are also known as “bacon flies” and their larvae as “bacon skippers”, “ham skippers”, “cheese maggots”, “cheese hoppers”, etc.

The adult cheese fly’s body is black, blue-black, or bronze, with some color on the head, antennae, and legs. The wings are faintly iridescent and lie flat upon the fly’s abdomen when at rest. At 1/6 inch long, the fly is smaller than the common housefly.

The waltzing fly, Prochyliza xanthostoma, occurs in Northern America and is in the same family as the cheese fly. It is one of the carrion-feeding Piophilidae and is remarkable for its sexual dimorphism and its patterns of behavioral adaptation and associated morphological adaptations. In particular the antennae, forelegs and heads of the males are adapted to their behavior in combat and courtship.

The waltzing fly breeds in early spring, specifically on the carcasses of moose. By mid-spring of a good year, they are one of the most abundant insect species in the local forests. Nubile females bask on vegetation around carcasses, and males aggregate in their sun to court and to defend territories. Two competing males will fight, each striking the other with his head and antennae. Such fights may last for several minutes, a long conflict for such small creature.