Mezcal, or mescal is a distilled alcoholic beverage made from the maguey plant.
It is unclear whether distilled drinks were produced in Mexico before the Spanish Conquest. The Spaniards were introduced to native fermented drinks such as pulque, also made from the maguey plant. Soon the conquistadors began experimenting with the maguey plant to find a way to make a distillable fermented mash. The result was mezcal.
Today, mezcal is still made from the heart of the maguey plant, called the "piña", much the same way it was 200 years ago, in most places. In Mexico, mezcal is generally consumed straight and has a strong smoky flavor. Though mezcal is not as popular as tequila (a mezcal made specifically from the blue agave in select regions of the country), Mexico does export the product, mostly to Japan and the United States, and exports are growing.
Mezcal is famous for the dead agave worm rolling around at the bottom of the bottle. The alcoholic strength of the contents is proved by the state of preservation of the worm, which is considered a powerful aphrodisiac for Zapotecan Indians. Alas, like most aphrodisiacs, it's all hype and the worm is really just a marketing gimmick.
The worm is usually soaked in pure alcohol before being added to the bottle of mezcal to preserve the worm, some say the worm changes the taste of the drink.
Another variety of worm added to Mezcal is actually the larva of a weevil which can cause a great amount of damage to maguey crops, the damage is caused a bacteria rather than the weevil its self.