The larvae of the cheese fly (Piophila casei) are deliberately introduced to pecorino cheese, where their digestive action produces an advanced level of fermentation, including a breakdown of the cheese’s fats. The cheese’s texture softens, and a liquid called làgrima (‘teardrop’) may seep out.

It’s eaten with the maggots still in it

Because the larvae in the cheese can launch themselves distances up to 15 centimetres (6 in) when disturbed,[7][14] diners hold their hands above the sandwich to prevent the maggots from leaping.[11][12]