At the bottom of some mezcal bottles sits one of the most famous curiosities in the world of spirits. It’s a pale, curled-up “worm” preserved in alcohol. It’s helped give mezcal an air of mystery for decades, but scientists have now shown that this famous bottle stowaway isn’t a bug at all.
Mezcal is a distilled spirit made from agave, the same plant group used to make tequila. Most bottles are sold without any additions, but a small number contain larvae known as gusanos de maguey (Spanish for agave worm). Although this tradition feels ancient, it’s actually much newer than mezcal itself. Although mezcal production in Mexico dates back centuries, the practice of placing the larvae in bottles appears to have started in the 1940s.
The age-old mystery of mezcal
For many years, the identity of these larvae remained unknown. They were described as moth larvae, butterfly larvae, and even weevil larvae. Some suspect that more than one species is involved, especially since the bottled “worms” can vary in color and appearance.
“It’s relatively easy to roughly determine the type of larva based on the shape of its head, but its identity has yet to be confirmed,” said Akihito Kawahara, curator at the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum. “This is probably because most biologists don’t look inside mezcal bottles.”
To answer this question, Kawahara and his colleagues studied mezcal gusanos in a study published in 2023. PeerJ’s life and environment. In 2022, the team traveled to Oaxaca, Mexico, a region heavily associated with mezcal production. They visited distilleries, collected as many different brands as they could find, and sampled larvae from various bottles.
The larvae didn’t provide many obvious clues. After sitting in alcohol, their bodies were preserved, but many visible characteristics that could help identify them were limited. But its preservation also protected something far more useful: DNA.
DNA reveals surprising answers
Researchers were able to extract and analyze genetic material from 18 specimens. They expected that because Gusanos de Maguey is harvested from the wild rather than being bred through a standardized commercial system, the results could represent several different insects.
One of the main suspects was Tequila’s giant captain (Aegial Hesperias), a butterfly whose caterpillars feed on agave plants. Its large, whitish larvae looked a lot like the many pale gusanos found in mezcal bottles. The name made it an obvious candidate.
But DNA told a different story. All larvae that produced available genetic data matched the agave redworm moth (Comadia Lettenbacheri). in Peer J The study also identified specimens that did not produce usable DNA as morphologically the same species.
This finding suggests that the mezcal “bugs” are not a random mixture of agave insects. At least in the jars sampled, it was consistently a single species of moth caterpillar. The researchers also proposed an explanation for the pale, “white worm” appearance reported on some bottles: larvae that spend too much time in alcohol can lose some of their reddish color over time.
Why is this tiny larva important?
This discovery comes as mezcal continues to grow far beyond its traditional market. Consumer interest in artisanal spirit and small-batch production has increased its popularity internationally.
That growth poses difficult problems. While tequila is often produced on an industrial scale, mezcal is still commonly produced in small-scale facilities in Mexico’s arid countryside. Producers roast the round agave cores in fireplaces or kilns, crush and ferment the cooked material, and then distill it in small batches. As demand increases, it remains unclear whether all growers, landowners and the agave ecosystem can scale up without long-term harm.
The same concerns apply to the agave redworm moth. Its larvae, also known as chiniquills, have been eaten in Mexico for centuries and are an important part of traditional cuisine. However, wild collection can be intense, and insects are not simply collected from the surface of the plant. Red agave caterpillars create tunnels through the center of their host agave plants, and collecting them often causes the plants to die.
“Agave worms are still fairly common, but because mezcal is harvested in the wild, the effects of mezcal proliferation could have long-term negative effects on local populations,” Kawahara said.
New study adds warning
Recent research has further raised concerns about sustainability. A 2025 study in Botanical Sciences investigated chiniquill extraction from agave aplanata populations and found that populations without extraction had higher growth rates. The study reports that larval harvesting can reduce agave populations by up to 57 percent, and that young plants are particularly affected because they are often harvested for their larvae, despite their importance to population survival.
Although that study focused on agave populations rather than mezcal bottles, it reinforces the same broader issue: the market for edible agave larvae can affect both insects and the plants they depend on. The study also noted that harvesting requires sacrificing the agave plants before they reach sexual maturity, which could alter future population dynamics.
For mezcal producers and harvesters, it can make sustainable production more complicated. If demand for bottles containing gusano continues to increase, local communities may need better ways to manage wild harvests, raise larvae on agave farms, and develop ways to produce gusano without destroying host plants.
Mezcal worms may have started out as a marketing novelty, but thanks to DNA, they’ve turned into something much more interesting. It’s a small creature with a clear identity, a deep connection to the agave landscape, and a future tied to how mezcal’s growing popularity is carefully managed.
