What is "casu marzu"

n. A cheese dish from Sardinia, riddled with insect larvae.

Casu marzu (also called casu modde, casu cundídu and casu fràzigu in Sardinian language, or in Italian formaggio marcio), literally translating into English as "rotten / putrid cheese", is a traditional Sardinian sheep milk cheese, notable for containing live insect larvae (maggots). Although found mostly in the island of Sardinia, the cheese is also found in the nearby Corsica, where it goes by the name of casgiu merzu.

Derived from Pecorino, casu marzu goes above and 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 and breaking down of the cheese's fats. The texture of the cheese becomes very soft, with some liquid (called lagrima, Sardinian for " tears") seeping out. The larvae themselves appear as translucent white worms, about long.

When disturbed, the larvae can launch themselves for distances up to . Some people clear the larvae from the cheese before consuming while others do not.

The cheese, along with one of its Sardinian makers, Giovanni Gabbas, received attention on the US TV program Bizarre Foods with Andrew Zimmern. Zimmern described the taste of the cheese as "so ammoniated" that "it scorches your tongue a bit." The cheese is known to leave an aftertaste for a duration of up to several hours.