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.
That finding suggests the mezcal “worm” is not a mix of random agave insects. At least in the sampled bottles, it was consistently the caterpillar of a single moth species. The researchers also proposed an explanation for the pale “white worm” appearance reported in some bottles: larvae that spend long periods in alcohol may lose some of their reddish color over time.
Why This Tiny Larva Matters
The discovery arrives as mezcal continues to grow far beyond its traditional markets. Its popularity has surged internationally, helped by consumer interest in artisanal spirits and small batch production.
That growth raises difficult questions. Tequila is often produced at industrial scale, but mezcal is still commonly made in smaller facilities across Mexico’s dry countryside. Producers roast the rounded hearts of agave plants in fire pits or kilns, then crush and ferment the cooked material before distilling it in smaller batches. As demand rises, it remains unclear whether all producers, landowners, and agave ecosystems can scale up without causing long term harm.
The same concern applies to the agave redworm moth. Its larvae, also known as chinicuiles, have been eaten in Mexico for centuries and are an important part of traditional cuisine. But wild harvesting can be intense, and the insects are not simply picked from the surface of a plant. Red agave caterpillars tunnel into the core of their host agaves, and collecting them often kills the plant.
“Agave worms are still fairly common, but the impact of mezcal becoming popular can have long-term negative effects on local populations because they are harvested in the wild,” Kawahara said.
Newer Research Adds a Warning
More recent research has sharpened the sustainability concern. A 2025 study in Botanical Sciences examined chinicuil extraction from Agave applanata populations and found that populations without extraction had higher growth rates. The study reported that larvae extraction could reduce agave populations by up to 57 percent, with juvenile plants especially affected because they are often harvested for larvae even though they are important for population persistence.
That work focused on agave populations rather than mezcal bottles, but it reinforces the same broader issue: the market for edible agave larvae can affect both the insect and the plant it depends on. The study also noted that harvesting can require sacrificing the agave before it reaches sexual maturity, which can alter future population dynamics.
For mezcal producers and harvesters, that could make sustainable production more complicated. If demand for bottles containing gusanos continues to rise, local communities may need better ways to manage wild harvesting, raise larvae on agave farms, or develop methods for producing them without destroying host plants.
The mezcal worm may have started as a marketing novelty, but DNA has turned it into something more interesting: a small creature with a clear identity, a deep connection to agave landscapes, and a future tied to how carefully mezcal’s growing popularity is managed.
