By Josh Lancette
Researchers in Panama have discovered a new species of fly in the family Chloropidae. The name of the new species is Pseudogaurax paratolmos, as reported in a recent paper published in Annals of the Entomological Society of America.
While a new species is interesting enough by itself, the researchers discovered something unique about this fly: it is the first known member of its family to parasitize ants. With this discovery, there are now four fly families that are known to parasitize ants (the other three are Tachinidae, Syrphidae, and Phoridae).
The new fly species was found to be an ectoparasitoid of the larvae of Apterostigma dentigerum, a fungus-growing ant. These ants culture fungi under logs, bark, or stones, and then use the fungi as food.
While studying these ants, the researchers discovered fly larvae attached to and feeding on the ant larvae.
“We were studying dynamic diseases management in the fungus-growing ants, and in Apterostigma we were focused on the dynamic interactions between macroparasites (parasitoid wasps) and microparasites (Escovopsis and entomopathogens),” said Dr. Hermógenes Fernández-Marín, one of the co-authors. “We were surprised to find in the Apterostigma dentigerum nests that there were fly larvae stuck to ant larvae, because ants are extremely careful to tend to the brood and discriminate against larvae with parasites.”
“We were surprised at the brood-care behavior of the ant, how workers groomed all larvae without discriminating between healthy larvae and sick larvae,” continued Cely Gonzalez, a PhD student and one of the co-authors.
However, it isn’t known how the parasitoids seem to go undetected.
“With these chloropid flies, because they develop on the outside of the ant larvae, it raises the question of how the parasitoid is able to evade detection by the ants and not be killed,” said Dr. Ann Fraser, an associate professor of biology at Kalamazoo College who was not involved with the research. “Does it acquire the taste and smell of the ant brood, or can it produce the necessary chemical signatures on its own?”
While Pseudogaurax paratolmos is the first known parasitoid of ants in its family, it appears to only parasitize one ant species.
“We conducted an extensive sampling from three Apterostigma ant nests in central Panama, and we found that only this one species was attacked by flies, while two other ants species that are equally abundant were not parasitized,” said Dr. Fernández-Marín.
If it does only parasitize one species, it could be a risky survival strategy.
“This new discovery also raises the question of how species-specific these parasitoids are,” said Dr. Fraser. “Can they successfully attack only a single ant species, as this study seems to suggest? If so, these flies are really putting all their eggs in one basket!”
Besides being an interesting biological find, this new study might also have implications for biocontrol.
“This discovery enlarges the number of fly families known to attack ants and raises questions about how common this lifestyle is among these flies,” said Dr. Fraser. “It may also enlarge the arsenal of biocontrol agents available for pest management should some of these flies attack pest ant species.”
While this new discovery is interesting on multiple levels, even more discoveries will likely be made in the future, according to Gonzalez.
“Panama is a biodiversity hot spot,” she said. “Many studies about the biology of the fungus-growing ants have been conducted in Panama, so it is impressive how such parasitoids can still be unknown.”
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Josh Lancette is Manager of Publications at the Entomological Society of America.