Scientific inspiration can strike anywhere, even in a bar-restaurant in Oaxaca, Mexico. It was there that a team of insect researchers decided to use DNA sequencing to identify the larvae hiding in the bottles of the country’s signature alcohol, mescal.
“We were taking a break, we were in a restaurant, and then we just saw these bottles,” says Akito Kawahara, lead author of the new research and curator of butterflies and moths at the Florida Museum of Natural History. “One thing led to the next, and we started thinking about what the larva is.”
And in an analysis of nearly two dozen liquor bottles, scientists determined that all the mescal ‘worms’ they tested belonged to a single species of mothaccording to their study published on March 8 in PeerJ. Finding just one species was a bit surprising, Kawahara says, because he and his colleagues had identified three main suspects, all of which are agave plant parasite larvae that are processed to create mescal: a butterfly called the giant skipper tequila (Aegiale hesperiaris), the agave snout weevil, (Scyphophorus acupunctatus) And Comadia redtenbacheri, a butterfly whose juvenile form is known as the red agave worm. It was this last species that turned out to be the mystery larva.
Mescal is closely related to tequila, which is made exclusively from a specific variety of agave, whereas mescal can be made from many species. Tequila never includes worm, but mescal can. It’s a marketing tactic that nods to Mexico’s strong insect-eating culture (the country is home to more than 400 edible species). Anne Gschaedler, a researcher at the Center for Research and Assistance in Technology and Design of the State of Jalisco (CIATEJ) in Mexico, who was not involved in the new study, says that today mescal with a worm is more sought after by non-Mexicans than locals, however.
Some scientists who were not involved with the article found its discovery predictable. “The results are hardly surprising,” said Ricardo Castro-Torres, an entomologist at the Postgraduate College in Mexico, in an email to American Scientist. “In my opinion, there really is a consensus on the species included in mescal bottles.” (Kawahara notes that the new study is the first genetic analysis of mescal worms and that previous research he reviewed was unclear about the identity of the species.)
Researchers have long known that C. redtenbacheri lays its eggs on agave plants. The larvae tunnel into the fleshy base of the plant to grow, grow (and blush distinctly) before turning into a cream-colored moth and leaving the plant. “These are quite unusual moths,” Kawahara says, referring to the color change.
For the new study, Kawahara and his colleagues collected 21 bottles of mescal from 18 different manufacturers, pouring each bottle through a sieve to catch the “worm.” (A real worm stays restless throughout its life, but the three mescal worm contenders are larvae waiting to metamorphose into their adult form.)
Then the researchers studied each specimen directly and took a piece of its chest for DNA sequencing. Luckily for the bar sleuths, mescal is an ideal environment to taste because alcohol helps preserve genetic material. Ultimately, genetic analysis identified 18 of the samples as C. redtenbacheri. The researchers were unable to obtain DNA samples from three of the worms, likely because these worms had been cooked before being placed in the mescal, they wrote. These specimens corresponded morphologically to the red agave worm.
The study may not be good news for wild red agave worms. Kawahara says these larvae are getting harder and harder to find. C. redtenbacheri moths depend exclusively on agave plants for most of their life cycle, even as the local environment changes and the demand for mescal and agave is increasing. More mescal production could mean more agave plants for worms, but crop damage (especially from the agave snout weevil, which was a pretender to the mescal worm’s identity) could bring growers to start using pesticides in earnest.
“If demand continues as it has been, that worries me,” Kawahara says. “Even though the moth isn’t necessarily endangered or threatened or anything like that at this point, the possibility that this sort of thing could happen is definitely there.”