The grain moths have finally reached Antarctica

These common household pests are known to infest food all over the world.
Indian Meal Moth
A recent sighting, right off the northwest coast of the Antarctic Peninsula, is the furthest south the species has ever been documented. DepositPhotos

Last February, researchers at an Antarctic research station spotted something alarming: a moth.

Normally, a moth is not a particularly frightening sight. But in Antarctica, where there are no native moths, spotting the insect could only mean one thing—a non-native species had been introduced to the continent. To make matters even more interesting, the moth in question turned out to be Plodia interpunctella, commonly known as the Indianmeal moth or the grain moth, a common household pest worldwide.

In the past few years, grain moths have been spotted at a few different research stations around Antarctica, slowly moving further south. So far, the insects have had a limited impact on the field stations, and scientists believe they are likely unable to survive for very long in the harsh, cold climate of the frozen continent. But this recent sighting, right off the northwest coast of the Antarctic Peninsula, is the furthest south the species has ever been documented—and a reminder of the growing threat that invasive species pose to Antarctica’s fragile ecosystem, especially as the climate continues to warm.

“Any non-native insect poses a potential threat to Antarctic biodiversity,” Hugo Benitez, a researcher at the Universidad Católica de Maule, Chile and the Millennium Institute of Antarctic and Subantarctic Biodiversity, told PopSci via email.

If you’ve ever kept dry food unsealed, you’ve probably encountered a grain moth. The small brown and white insects often lay their eggs in grains like oatmeal, rice or flour, where they wiggle around as larvae and eventually develop into adult moths that flutter about in our pantries and cupboards. While the creatures can’t survive very long in the cold, they can survive indoors in many cold climates, and the species has seamlessly spread across the Americas, Europe, Africa, Asia, and Australia.

Despite this ubiquity, as of a few years ago, grain moths had never made it to Antarctica.. But in 2017 and 2021, the moths were first spotted at Korean and Brazilian research stations in the South Shetland Islands, making these individuals the first of their species to be seen in the Antarctic Peninsula region and the first to be seen below 60° S, the area officially covered by the Antarctic Treaty. The sighting last February, at Chile’s Yelcho station on Doumer Island, took place a full 150 miles south of the 2017 and 2021 spottings—and it may only be a matter of time before the moths show up at one of the many other research stations along the peninsula.

After their initial moth spotting (and another one two days later), the researchers caught the insects and later sequenced their DNA to confirm the species as Plodia interpunctella. The team, including Benitez, published a record of this sighting earlier this month in the journal Ecology and Evolution.

For now, the researchers believe that Antarctica is too cold for the grain moths to spread in the wild. But the moths could continue to show up at additional field stations, creating potential headaches if they were to lay eggs in the stations’ food–and adding to the “logistical difficulties inherent in supplying and storing food for Antarctic research stations,” the authors write.

In addition, the moths could bring other unwanted creatures with them. The new paper notes that grain moths can be a host species for Habrobracon hebetor, a parasitoid wasp that lays its eggs in the moth’s larvae. If that wasp were to somehow make it out of the field stations and parasitize Belgica antarctica, a small midge and the only insect native to the continent, the results could be “disastrous,” the authors write.

Even beyond grain moths, invasive species are a growing concern for conservationists and scientists working in Antarctica. Despite the harsh climates and punishing winters, animals like mites and flies, as well as plants like bluegrass, have made it to the far south in recent decades, probably introduced by humans. Most of these introductions have been limited to the sub-Antarctic islands and the Peninsula region, which are warmer than the rest of Antarctica. If these regions warm even further with climate change, that could also make these habitats much more hospitable for newcomers.

And in Antarctica’s terrestrial ecosystems, even a small non-native animal could wreak havoc. Unlike the marine ecosystem around the continent—which is filled with all kinds of charismatic wildlife like penguins, fish, krill and whales—land-based life in Antarctica is sparse and specialized. In addition to Belgica antarctica, the terrestrial ecosystem is composed of just a handful of small animals like springtails (a type of tiny arthropod), a smattering of microorganisms and low-lying ground cover such as lichen. 

With such a unique ecological community–especially one shaped by millennia of isolation–newcomers like grain moths could have an outsized impact. But non-native species can also be caught before they cause trouble. Benitez said that “biosecurity” measures like quarantining and inspecting cargo are necessary, and could catch stowaways like grain moths before they reach the continent.

“Early detection,” he said, “is crucial for effective intervention.”