Sigh. Why is it that whenever insects and food go together, people immediately go for the shock value?

Boing Boing recently ran a post titled “Maggot Cheese that tries to Eat Your Eyes.”

“Casu marzu is an illegal Sardinian cheese that is served riddled with writhing maggots that try to jump into your eyeballs as you eat it.”

That is, of course, not the case at all.  It is cheese, and it is riddled with maggots (which is why it is also illegal). But the maggots are not crazed eye-seeking missiles; they are insects known as cheese skippers.  They get the name “skipper” because the larvae can jump up to 15 cm.

So, they could, potentially, jump into your eyes. But that isn’t where they are aiming–in fact, they don’t aim much at all. The larvae “flip” to escape from a predator or parasite that disturbs them.  You can see a lovely video on how the cheese is made here. The actions of the maggots make the cheese nice and runny.

Interestingly, like the Scientific American Fiasco, you can trace coverage of this very maggoty cheese (even I might not eat it, which should tell you something) through the filter of the internet:


So, what are these cheese skippers, anyway?

There is a very entertaining profile of the fly and its relatives here, from a professor that studies them. (He is the author of this paper, BTW.)

These flies are attracted to decomposing protein, and away from humans, they are important in the decomposition of dead animals.  These flies are also used in forensic entomology to date corpses and determine what habitat they may have been left in. (You’ll find them mentioned in Lee Goff’s book A Fly for the Prosecution.)

When humans conveniently supply protein-rich food products (another name for cheese skippers is “bacon fly”),  flies will move in and happily lay eggs.

There is not a lot of current, non-technical information about the cheese skipper online, although there are lots of charming publications from the 1900’s available.  This is probably why the Wikipedia article was relied on so heavily as a source in the posts I linked to above.  The best recent coverage of the cheese skipper for a general audience is in May Berenbaum’s book “99 More Maggots, Mites, and Munchers.

Could they hurt you?

It’s a probability thing. As I stated above, the maggots could hit your eyes, but that’s incredibly unlikely. And they certainly aren’t aiming for them, nor would they burrow into your eyes if they hit them.  There also is a potential for the maggots to survive the trip through your stomach, and then pierce your intestines with their mouth hooks, although most of the reports of that happening seem to stem from 1912 or  1922.

Random and Intriguing side tidbit: apparently cheese skippers were an important part of a 16th century heretic’s view of creation:

“Menocchio said: “I have said that, in my opinion, all was chaos, that is, earth, air, water, and fire were mixed together; and out of that bulk a mass formed- just as cheese is made out of milk- and worms appeared in it, and these were the angels. The most holy majesty decreed that these should be God and the angels, and among that number of angels there was also God, he too having been created out of that mass at the same time, and he was named lord with four captains….”

The book covering this hallucinating miller is interesting enough, it needs its own post!

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!


  1. Beware…the maggots have nasty, pointy teeth…
    ::flexing fingers in front of mouth::…Rarrggghhh!
    they’ll tear your throat out!

  2. Yeesh. It’s not exactly like you need to invent new dangers to get shock value here. That cheese is quite horrifying enough as is.

  3. I became aware of casu marzu about a year and a half ago through a comment someone left on one of my blog postings about cheesmaking. I’ve done a bit of follow up (the initial link that my friend sent me was the same Wikipedia article that you link to). Like you, I can’t find much decent information out there. I have come across references that suggest the potential for genuine health problems stemming from the fact that the larvae have surprisingly good survival in the digestive tract. They have strong mouth hooks that can breach the intestinal lining, leading to sepsis. So Phantom Midge’s suggestion may actually not be far off, though the problem occurs lower than the throat. The Museum of Hoaxes has a brief and very general post about it (verdict: not a hoax) that contains a link to an amusing piece on armywormm wine. Now that’s some wine and cheese party.

  4. Piophilidae on Tree of Life:

    A very interesting and cute little family of flies. Interesting facts: The first time senescence was proven to be a cost of mating in a wild population was using a piophilid, Protopiophila litigata (Bonduriansky, R. and C. E. Brassil. 2002. Nature 420:377). Another piophilid species, Neottiophilum praeustum, are haematophagous ectoparasites of baby birds as larvae, which is a pretty unusual life history for flies. Lastly, the way the larvae jump is probably singular among flies. They hook their mandibles into their backside, flex, and flip in the air when the mandibles dislodge. The technical term for this is ‘sproinging,’ apparently. There’s more about their biology in Manual of Nearctic Diptera Vol. 2 (Research Branch Agriculture Canada, 1987).

  5. Keith–they sound like a fascinating group. I’m almost ready to throw over moths for a new research animal!

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