{{Short description|Species of fly}} {{About|the fly species|the family|Piophilidae}} {{Speciesbox | name = Cheese fly | image = Piophila casei british entymology detail.jpg | image_caption = ''Illustration of Piophila casei'' | taxon = Piophila casei | authority = (Linnaeus, 1758) }} 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 sardo cheese to produce the characteristic ''casu martzu''.
If consumed by humans, the larvae have a chance to survive in the intestine, causing enteric pseudomyiasis,<ref>{{cite journal|last1=Peckenscneider |first1=L. E. |last2=Polorny |first2=C. |last3=Hellwig |first3=C. A. |date=May 17, 1952 |title=Intestinal infestation with maggots of the cheese fly (Piophila casei) |journal=JAMA |volume=149 |issue=3 |pages=262–263 |doi=10.1001/jama.1952.72930200005011b |pmid=14927333 }}</ref> though no such cases have been linked to ''casu martzu'' dishes.<ref name=CNNtravel>{{cite web|last=Petroni|first=Agostino|url=https://www.cnn.com/travel/article/casu-marzu-worlds-most-dangerous-cheese/index.html|title=Casu marzu: The world's 'most dangerous' cheese|website=CNN Travel|date=18 March 2021|access-date=12 March 2025|others=Lead photo by Andrea Serreli}}</ref> The larvae may also carry harmful microorganisms that, when consumed, could cause infections.<ref name="Europarl-2024">{{Cite web |date=2024-01-15 |title=Subject: Petition No 0702/2023 presented by Nicolò Quartararo (Italian) on restoring the status of Casu Marzu cheese as a foodstuff and edible product in the EU |url=https://www.europarl.europa.eu/doceo/document/PETI-CM-758761_EN.pdf |url-status=live |archive-url=https://web.archive.org/web/20240608022912/https://www.europarl.europa.eu/doceo/document/PETI-CM-758761_EN.pdf |archive-date=2024-06-08 |archive-format=PDF |access-date=2024-06-08 |publisher=European Parliament}}</ref>
==Description== Adult male cheese flies are usually {{cvt|4.4–4.5|mm}} long, with females slightly larger at {{cvt|5.0–5.2|mm|3}} long. The body is primarily a metallic black bronze in color, 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, with yellow patches on the lower face.<ref name=":2">{{cite book |last1=Scholl |first1=Philip J. |chapter=Chapter 19: Myiasis (Muscoidea, Oestroidea) |date=2019-01-01 |title=Medical and Veterinary Entomology |edition=3rd |pages=383–419 |editor-last=Mullen |editor-first=Gary R. |url=https://www.sciencedirect.com/science/article/abs/pii/B9780128140437000194 |access-date=2025-04-04 |publisher=Academic Press |isbn=978-0-12-814043-7 |last2=Colwell |first2=Douglas D. |last3=Cepeda-Palacios |first3=Ramón |editor2-last=Durden |editor2-first=Lance A.}}</ref> 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.
== Life history == Larvae have three instars, with late-instar larvae capable of greatest dispersal. When fully grown, they are {{cvt|9–10|mm}} long, {{cvt|1|mm}} wide, and have 13 segments. When disturbed, or dispersing to sites for pupation, the larvae can leap {{cvt|10–12|cm}} by hooking their mouths into a nearby surface or into their own posterior segments, contracting their muscles, and releasing, flinging themselves forward—this locomotion technique is believed to be what has led to the name "cheese skippers".<ref name=":0">{{Cite web |last1=Lewis |first1=Caitlin |last2=Kaufman |first2=Phillip |date=January 2010 |editor-last=Gillett-Kaufman |editor-first=Jennifer |title=Cheese Skipper |url=https://edis.ifas.ufl.edu/publication/IN843 |access-date=8 May 2025 |website=Featured Creatures collection |publisher=Entomology and Nematology Department, University of Florida}}</ref><ref name=":2" />
Larvae are detritivores, feeding on protein rich sources, including meats, cheeses, and carrion. They seek out dark, dry areas for pupation, which lasts around 12 days.<ref name=":0" /> Adult larvae can overwinter before pupation.<ref name=":2" />
In cases of myiasis, larvae that are embedded in unrefrigerated meats and cheeses can be ingested, then pupate and emerge as adults while still in the host's alimentary tract.<ref name=":2" />
== Cheese flies and food safety == ''P. casei'' are considered pests in the meat and cheese industries. Female cheese flies lay eggs on meats and cheeses, which, when hatched, produce burrowing larvae that are difficult to detect in food products until they grow large enough to disperse.<ref name=":1">{{Cite journal |last1=Jones |first1=Billy Ray |last2=Graham |first2=Paul P. |last3=Kelly |first3=R. F. |date=1971-08-01 |title=Microorganisms as inducers of oviposition for the cheese skipper, ''Piophila casei'' (L) diptera |url=https://www.sciencedirect.com/science/article/pii/S0362028X23021038 |journal=Journal of Food Protection |volume=34 |issue=8 |pages=410–415 |doi=10.4315/0022-2747-34.8.410 |issn=0362-028X|url-access=subscription }}</ref>
Research conducted on methods for preventing the oviposition and larval infestation of ''P. casei'' in cured meats and cheeses suggests the use of certain plant essential oils, from plants such as ''Mentha canadensis'', to prevent larval growth.<ref name=":1" /> Alternatively, regulating the microbiome present in food processing facilities can remove the microbial symbionts of ''P. casei'', whose metabolic wastes provide food for ''P. casei'' larvae.<ref>{{Cite journal |last1=Bi |first1=Shenghui |last2=Liu |first2=Linggao |last3=Jia |first3=Mingxuan |last4=Feng |first4=Bingxia |last5=Wan |first5=Jing |last6=Zhou |first6=Ying |last7=Liu |first7=Yuanyuan |last8=Liu |first8=Jianfeng |last9=Zhu |first9=Qiujin |date=2023-11-01 |title=Exploring insecticidal properties and acetylcholinesterase inhibition by three plant essential oils against the cheese skipper ''Piophila casei'' (Diptera: Piophilidae) |url=https://www.sciencedirect.com/science/article/abs/pii/S0926669023009639 |journal=Industrial Crops and Products |volume=203 |article-number=117198 |doi=10.1016/j.indcrop.2023.117198 |issn=0926-6690|url-access=subscription }}</ref>
== References == {{Reflist}}
==External links== *[http://www.phorid.net/diptera/schizophora/piophilidae/piophilidae.html Image of ''Piophila casei''], Los Angeles County Natural History Museum
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Category:Insects described in 1758 Category:Piophilidae Category:Animal taxa named by Carl Linnaeus Category:Flies of New Zealand
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