Newly described species of giant fly and soldier fly resemble hornets
January 06, 2016
By Peter Moon | Agência FAPESP – Entomologists believe that there are a million species of true flies in the world. True flies are insects of the order Diptera and include horse flies, black flies, mosquitoes, midges and gnats. Only approximately 160,000 species have been described. Twelve thousand of them live in Brazil, and the number of known Brazilian species is steadily increasing. In November alone, nine new species of soldier fly and two new species of giant fly, the world’s largest flies, were described in two different papers. The research projects in these papers were funded by FAPESP under its BIOTA Program.
The largest known fly in the world is Gauromydas heros, a Brazilian species. This magnificent insect, a member of the Mydidae family, measures 6 cm from the tip of its abdomen to the top of its head (in contrast, common house flies are only 0.5 cm long). “Giant flies measuring as much as 7 cm have been observed,” said Julia Calhau, a zoologist who has studied flies since 1998 and giant flies in particular since 2009, at the University of São Paulo’s Zoology Museum (MZ-USP).
“I’ve only seen G. heros once. It was in 2000, in the Rio Doce State Park in Minas Gerais. It was alive, but I failed to catch it. They’re very nimble,” said Calhau, who is currently conducting postdoctoral research at the Federal University of Grande Dourados (UFGD) in Dourados, Mato Grosso do Sul.
Until recently, only four species of the genus Gauromydas were known, all of which are native to South America. The newest members of the genus are G. mateus and G. papaveroi, which have recently been described by Calhau and two colleagues in the journal Zootaxa. The project was supported by FAPESP.
According to Calhau, G. papaveroi measures 4 cm and is found in Pará, Amazonas and Santa Catarina, Brazil, as well as in Argentina and Costa Rica. G. mateus is slightly smaller, measuring 3.5 cm. This species is found only in the Salta region of northern Argentina.
“They’re extremely rare creatures,” Calhau said. “Giant flies spend most of their lives as larvae. Their adult phase is very short.” Very little is known about the habits of the two new species, and practically all that is known has been inferred from studies of G. heros published in the 1940s by Czech entomologist José Francisco Zikán, who emigrated to Brazil in 1902 and studied the species for 40 years in Itatiaia National Park in Rio de Janeiro State.
According to Zikán, giant-fly larvae live inside the nests of leafcutter ants of the genus Atta. “Leafcutters build waste disposal chambers in or near their nests, and some creatures live off this waste, such as moth larvae and beetle larvae. Apparently, larvae of Gauromydas prey on these other larvae,” Calhau said.
Confused with wasps
Mydas flies, as Gauromydas giant flies are also known, have long been confused with wasps and hornets because of their size and appearance, Zikán wrote in 1942. Superficially, they do resemble hornets. “However, they’re completely harmless and feed on flower nectar,” Calhau explained. “They neither transmit disease nor have economic or agricultural importance, but they’re magnificent creatures.”
Soldier flies, the other group of Diptera for which new species were recently described, belong to the genus Acrochaeta Wiedemann in the Stratiomyidae family. Diego Aguilar Fachin, a doctoral student in entomology at the University of São Paulo’s Ribeirão Preto School of Philosophy, Science & Letters (FFCLRP-USP), has recently described nine species of soldier fly in a paper also published by Zootaxa. “They’re called soldiers for two reasons. Some have green-and-black stripes on their abdomens, recalling a military uniform, and some have bristles that look like armor,” said Fachin, whose research was supported by FAPESP.
Eight of the species described by Fachin join 335 species of soldier fly already known in Brazil. The ninth new species lives in Bolivia and Peru. Fachin worked with material collected for FAPESP’s BIOTA Program. Like giant flies, “soldier flies of the genus Acrochaeta closely resemble wasps,” Fachin said.
The newly described species have a narrow-looking waist that reminiscent of that of a wasp. “Soldier flies are large, ranging from 1.5 cm to 2 cm in length, with a wasp-like shape and coloring,” Fachin said. A possible explanation for this morphology, in his view, is that it may be a sort of camouflage, preventing the wasps they live close to from recognizing them as enemies. “I haven’t studied them in the field, but I suspect ‘my’ flies and wasps are next-door neighbors.”
The new species live in the Southeast region and in two Southern states – Paraná and Santa Catarina – as well as in Rondônia in the North. “The ones that I like most are A. polychaeta and A. pseudopolychaeta. They both have very long antennae, and the latter has a very long bristle full of shorter bristles,” Fachin said.
Like giant flies, the soldier flies described by Fachin are inoffensive despite their size and menacing appearance. They have no medical importance and are not pollinators. “This is why both groups have been neglected by researchers to some extent. However, they’re no less important for that,” he said.
The article “Review of the Gauromydas giant flies (Insecta, Diptera, Mydidae), with descriptions of two new species from Central and South America” (doi: http://dx.doi.org/10.11646/zootaxa.4048.3.3) by Julia Calhau et al., published in Zootaxa, can be read at http://biotaxa.org/Zootaxa/article/view/zootaxa.4048.3.3.
The article “Taxonomic revision and cladistic analysis of the Neotropical genus Acrochaeta Wiedemann, 1830 (Diptera: Stratiomyidae: Sarginae)” (doi: 10.11646/zootaxa.4050.1.1) by Diego Fachin et al., published in Zootaxa, can be read at http://biotaxa.org/Zootaxa/article/view/zootaxa.4050.1.1.
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