'Casu marzu' literally means 'rotten/putrid cheese'. It is a traditional Sardinian sheep milk cheese that contains live insect larvae (maggots).

'Casu marzu' goes beyond typical fermentation to a stage of decomposition, brought about by the digestive action of the larvae of the cheese fly 'Piophila casei'. These larvae are deliberately introduced to the cheese, promoting an advanced level of fermentation.

'Casu marzu' is created by leaving whole pecorino cheeses outside with part of the rind removed to allow the eggs of the cheese fly to be laid in the cheese. A female fly can lay more than 500 eggs at one time.

'Casu marzu' is believed to be an aphrodisiac by Sardinians. Because the larvae in the cheese can launch themselves for distances up to 15 centimetres (6 in) when disturbed, diners hold their hands above the sandwich to prevent the maggots from leaping.

Because of the European Union (EU) food hygiene-health regulations, the cheese has been outlawed. Some Sardinians organized themselves in order to make 'casu marzu' available on the black market, where it could be sold for double the price.

Attempts have been made to circumvent the EU ban by having 'casu marzu' declared traditional food. In 2005, a cooperation between sheep farmers and researchers of a local university developed a hygienic method of production aiming to allow the legal selling of the cheese.

More Info: en.wikipedia.org