Why do they put a worm in tequila and what is its significance in the drink?

The worm in tequila is actually found in mezcal, not tequila. The worm, which is actually a larva of a moth, is sometimes added to mezcal bottles as a marketing gimmick. It is not a traditional or necessary part of the drink. Some believe that consuming the worm brings good luck or has hallucinogenic effects, but there is no scientific evidence to support these claims.