Casu Marzu, an illegal Sardinian delicacy, is perhaps the most outrageously foul dairy product in our galaxy. While it's one thing to eat a cheese that smells like gym socks soaked in milk and left crumpled behind the toilet for weeks; you've entered a whole new class of repulsiveness when you bite into Casu Marzu -- a putrefied cheese infested with live, wriggling maggots.

To craft this noxious specialty Sardinian cheesemakers encourage the cheese fly, Piophilia casei, a.k.a. the "cheese skipper," to lay eggs in their pecorino cheeses. ("Pecorino" is a general Italian term for sheep milk's cheese.) One traditional method is to drill a hole in the block of cheese and slip in a drop of oil to attract the vermin. But the effort isn't always needed. While cheese skippers originally evolved to scavenge decomposed corpses, they've taken enthusiastically to the cured and fermented foods of Homo sapiens. Having discovered a suitable food supply, a mother will lay hundreds of eggs, which then hatch into a vile horde of hungry maggots, eager to devour their host environment.

In the case of Casu Marzu, these maggots -- legless and clawless, dragging themselves through by hooked teeth-- will release an enzyme during their digestion that causes the pecorino's fat to putrefy. This unique fermentation process yields a sticky, gluey, gummy mass, still teeming with the worms -- and ready to be eaten.

So, Just How Tasty Is It?

Once in your mouth, Casu Marzu is reported to cause more of a sensation than a "taste": a kind of oral-digestive riot, starting with a strong burn in the mouth. They say it's good with a full-bodied red, and doubles as an aphrodisiac. But what do "they" know, who eat larvae? As with most things, it's unclear who to trust. It is advisable when taking a bite of Casu Marzu to cover your eyes. This is not to protect your mind from the nauseating sight; but to protect the eyes themselves from the maggots, who can and do leap up to six inches off the cheese, with malevolent precision. (If you're too squeamish for such a confrontation, try sealing the cheese in a paper bag. The maggots, deprived of oxygen, will leap off the cheese in an attempt to escape; and when the pitter patter of their dying flops subsides, you can safely eat.)

Some people consider cheese skipper larvae a health risk, and Casu Marzu is actually illegal in Sardinia -- but this is not to say it can't be had. As a black market delicacy it is exchanged amongst family and friends, a favorite for weddings and birthday parties, and sold just under the radar at markets. Often, Sardinian heath officials are themselves fans of the cheese, appreciating its cultural significance, or its taste, or both.

Some Sardinian farmers still believe the medieval idea that maggots spontaneously generate in decaying cheese. This old theory created strong symbolic associations between cheese and death, but also decay and new life. It's even inspired weird cosmologies (Carlo Ginzburg writes about this in The Cheese and the Worms: The Cosmos of a Sixteenth-Century Miller). If you ever have the chance to try Casu Marzu, consider what it means to put the whole Circle of Life in your mouth at once. Then cover your eyes.

Cheese expert David Clark is guest blogging with us all week! Be sure to check out yesterday's post on Big Political Cheeses and the Riots They Caused.