Why is there a worm in tequila?

The worm in tequila is a marketing gimmick that originated in the 1940s to differentiate certain brands of mezcal. It is not a traditional practice in tequila production and is not found in all bottles of tequila. The worm is actually the larva of a moth that infests agave plants, which are used to make tequila. Some believe that consuming the worm can have hallucinogenic effects, but this is largely a myth.