The cheese fly, cheese skipper, or ham skipper (Piophila casei) is a species of fly from the family Piophilidae whose larvae are known to infest cured meats, smoked or salted fish, cheeses and carrion. On the Mediterranean island of Sardinia, the larvae are intentionally introduced into pecorino cheese to produce the characteristic casu martzu. If consumed by humans, the larvae have a chance to survive in the intestine, causing enteric myiasis,[1] though no such cases have been linked to casu martzu dishes.[2]
Adult male cheese flies are usually 4.4–4.5mm long, with females slightly larger at 5.0–5.2mm long. The body is primarily a metallic black bronze in colour, with two pale yellow iridescent wings that lie flat upon the fly's abdomen when at rest. The head has short antennae and red compound eyes. The legs are yellow-brown and are covered in short spines.
The cheese fly larvae are cylindrical and can appear white or cream, with black mouthparts. When fully grown, they are 9–10mm long, 1mm wide, and have 13 segments. When disturbed, the larvae can leap 10-12cm by hooking their mouths into a nearby surface and jerking forward - this is believed to be what has led to the name "cheese skippers".[3]