The worm is an agave worm, or gusano.

There is a lot of folklore surrounding the worm, with rumours that the worm is hallucinogenic, or a source of great heroism, or simply that the pickling of the worm is a proof of potency of the spirit. In any case, the eating of the worm is often made into a ritual of machismo...
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Worm frame grab
Frame grab from Worm
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