Cheese Skipper

Piophila casei (family Piophilidae) is a small, glossy blue-black fly, 3.5-4.5 mm long, with iridescent wings and pale-yellow face and legs. Females lay 100-500 eggs directly on high-protein, high-fat substrates such as cured meats, aged cheese, smoked fish, and carrion in advanced decay. Larvae are slender, tapering, cream-colored maggots reaching 8-10 mm; they are famous for 'skipping' — anchoring the mouth hooks to the posterior spiracles, arching the body, and releasing to launch up to 15 cm. Development from egg to adult takes 12-18 days under warm conditions, with pupation occurring away from the food source.

Adults are secretive, running rapidly over surfaces with short, jerky flights rather than sustained flying, and are strongly attracted to fermenting protein odors. Larvae burrow deep into the substrate, tunneling within cured hams and hard cheeses where surface inspection misses them. Larvae are of medical significance because ingestion of infested food can cause accidental enteric myiasis with abdominal pain and nausea; the larvae can survive stomach acid. In forensic entomology, P. casei colonizes remains during later decomposition stages and is used to estimate extended post-mortem intervals.