Mezcal worm in a bottle DNA test reveals a surprise

 At the bottom of some mezcal bottles sits one of the most recognizable curiosities in the world of spirits: a pale, curled "worm" preserved in alcohol. It has helped give mezcal an air of mystery for decades, but scientists have now shown that this famous bottle stowaway is not a worm at all.

Mezcal is a distilled drink made from agave, the same plant group used to produce tequila. Most bottles are sold without anything added, but a small number contain larvae known as gusanos de maguey (Spanish for agave worms). The tradition feels ancient, but it is actually much more recent than mezcal itself. While mezcal production reaches back centuries in Mexico, the practice of placing larvae in bottles appears to have begun in the 1940s.

A Longstanding Mezcal Mystery

For years, the true identity of these larvae remained uncertain. They had been described as moth larvae, butterfly larvae, and even weevil larvae. Some people suspected more than one species might be involved, especially because the bottled "worms" can vary in color and appearance.

"It's relatively easy to broadly determine the kind of larva based on the shape of the head, but their identity has never been confirmed," said Akito Kawahara, curator at the Florida Museum's McGuire Center for Lepidoptera and Biodiversity. "This is probably because most biologists are not looking inside mezcal bottles."

To settle the question, Kawahara and his colleagues studied mezcal gusanos in research published in 2023 in PeerJ Life & Environment. In 2022, the team traveled to Oaxaca, Mexico, a region deeply tied to mezcal production. They visited distilleries and gathered as many different brands as they could find so they could sample larvae from a variety of bottles.

The larvae did not offer many obvious clues. After sitting in alcohol, their bodies were preserved, but many visible traits that might help identify them were limited. That preservation, however, also protected something far more useful: DNA.

DNA Revealed a Surprising Answer

The researchers were able to extract and analyze genetic material from 18 specimens. They expected the results might point to several different insects, since gusanos de maguey are harvested from the wild rather than raised through a standardized commercial system.

One leading suspect was the tequila giant skipper (Aegiale hesperiaris), a butterfly whose caterpillars feed on agave plants. Its large, whitish larvae seemed like a strong match for many of the pale gusanos seen in mezcal bottles. Its name also made it an obvious candidate.

But the DNA told a different story. Every larva that produced usable genetic data matched the agave redworm moth (Comadia redtenbacheri). In the PeerJ study, specimens that did not produce usable DNA were also identified morphologically as the same species.

Source: ScienceDaily