In a new article published in the July issue of the Annals of the Entomological Society of America, Dr. Brian Brown of the Natural History Museum of Los Angeles presents a new discovery: a tiny fly species whose larvae can, Brown speculates, probably decapitate ants.
“It’s so small you can barely see it with the naked eye on a microscope slide. It’s smaller than a flake of pepper,” says Brown. “The housefly looks like a Godzilla fly beside it.”
The newly-discovered species, Euryplatea nanaknihali, belongs to family phoridae, which contains various types of small, hump-backed flies similar to common fruit flies. The new species of fly presented by Brown comes from Thailand. It is only around 0.40 mm long—five times smaller than the average fruit fly. This makes it the world’s smallest known fly.
“When you get really small like that, the environment changes,” Brown says. “The viscosity of air starts to become a problem and wind currents are major events. It’s amazing how small something can be and still have all of its organs. This is a new frontier, and publishing this tiny fly is basically a challenge to other people to find something smaller,” he adds.
Euryplatea eidmanni, a type of fly from Equatorial Guinea is the new fly species’ only known close relative. Euryplatea eidmanni, like some other members of family phoridae, is an ant parasite. The flies lay their eggs in the bodies of ants and the eggs hatch, releasing larvae into the ants’ bodies. These larvae feed inside of the ants’ heads and eventually escape after decapitating the ant from the inside.
Brown speculates that the newly-discovered fly species may be able to parasitize ant species that are inaccessible to larger flies such as Euryplatea eidmanni. Some of the world’s smallest ants have heads as small as 0.50 mm, making them very small targets for potential parasites. The larvae of many fly species would be too large to fit inside of these ants’ heads. The new species of phorid fly, however, is so small that it could parasitize such tiny ants. In fact, given the parasitic tendencies of its close relative, it seems likely that it does.
This phenomenon has not yet been directly observed, but Brown discusses the possibility in his paper, titled “Small Size No Protection for Acrobat Ants: World’s Smallest Fly Is a Parasitic Phorid (Diptera: Phoridae).”
“It had always been assumed that smaller species of ants would be free from attack because it would be physically impossible for flies that are 1-3 millimeters in length to develop in their relatively tiny heads,” he writes. “However, here we show that even the smallest host ants in a host-parasitoid system cannot escape parasitism.”
This fly species isn’t the only type of fly to decapitate ants from the inside. In 2007, researchers at Louisiana State University wrote about a phorid fly that lays an egg into the thorax of a fire ant worker. Eventually, the researchers concluded, the fly larvae release an enzyme to decapitate the ant. However, the Euryplatea eidmanni is unique because it can parasitize the world’s smallest ants whereas this type of fly must find a larger host.
National Geographic has several graphic pictures of a so-called “zombie” ant being decapitated by flies. Although Euryplatea eidmanni may be too small to use in the fight against fire ants, the USDA uses phorid flies to combat the invasive species of ant.
The world’s smallest known species of fly may still be useful to entomologists. According to Sanford Porter, an entomologist at the USDA, a variety of fly species are introduced in order to produce the desired effect on fire ant populations.
Further details about the new ant species and its possible role as a parasite can be found in this month’s issue of the Annals of the Entomological Society of America.