A new species of forcepfly with enormous genital pincers has been discovered in Brazil, bringing the total number of known species in this family to three. Plus a tiny fairyfly named Tinkerbella nana has been found in Costa Rica, and at 250 μm long, it's invisible to the naked eye, and one of the smallest insects in the world.

Affectionately described as "an inscrutable enigma to entomologists", almost nothing is known about the biology of the nocturnal and secretive forcepfly. We're not really sure how they live, what they eat, how they mate, and no one's ever seen one of their larvae. Adult forcepflies are very small, ranging from 10 mm to 20 mm, and their flattened bodies allow them to live under logs, bark and leaf litter, most often near stream or river banks. Like crickets and katydids, they can stridulate by rubbing its body parts together to attract a mate or ward off potential predators.

It's not known for sure what the function of their extraordinarily large terminal forceps is, but most researchers assume they're used by the males to grip onto the females during copulation. It's also been suggested that they could be used for fighting between male rivals, which has been observed their male relatives from the Panorpa genus of scorpionflies.

The first forcepfly species ever found was Merope tuber, discovered in eastern North America by British naturalist Edward Newman in 1838. Initially assumed to be very rare, American entomologist George W. Byers later discovered that they have quite an extensive range, from southeastern Canada to northern Georgia, west to Kansas, Minnesota, and eastern Iowa. M. tuber is the only known member of the Merope genus, most likely named after the dullest daughter of Atlas and Pleione in Greek mythology, and the wife of that guy who tricked this cat into minding his watermelon (for eternity).

Almost a century after M. tuber was discovered, another species was found, this time in the town of Yallingup in the Margaret River wine region of Western Australia. British entomologist, Frederick J. Killington, managed to collect just one individual of the species called Austromerope poultoni, and it took another 40 years for a second specimen to be found. In 1995, a fossilised, extinct species of forcepfly called Boreomerope antique was discovered in Siberia and dated to the Middle Jurassic period.

Now, a team from Texas A&M University, the National Institute of Amazonian Research and the Sao Paulo State University in Brazil, and led by entomologist Renato Machado, has discovered the third species in the Meropeidae family of forcepflies and the second species in the Austromerope genus. This pale, golden coloured species named Austromerope brasiliensis was named after its home near the Mata Atlântica forest of southeastern Brazil. It is the first forcepfly found in what's known as the Earth's Neotropical Zone, which covers all of South and Central American, plus the Mexican lowlands, the Caribbean islands, and southern Florida.

The existence of a South American forcepfly was predicted in 1973 by entomologist George W. Byers from the University of Kansas, who said that it could be the family connection between the North American and Australian species. In their recent paper published in ZooKeys, Machado and his colleagues come to the same conclusion through a comparison of all four known species of forcepflies.

First they paired the extinct genus of forcepfly, Boreomerope, with the North American Merope genus together, because they have so many similar morphological features, and then they paired the Australian and new Brazilian species together in the same genus, Austromerope. From this comparison, they suggested that the forcepflies had a common ancestor living on Pangaea 200 million years ago, and with the break-up of this ancient super-continent, the Meropeidae family was split into two main branches - one in the southern hemisphere, represented by the Austromerope genus, and one in the northern hemisphere, represented by M. tuber and the extinct B. antique. Which fits, because according to fossil evidence, B. antique existed in the northern hemisphere after Pangaea had split. "The widespread distribution of Meropeidae corroborates the fact that the family arose when all continents were connected," the team concludes.

And this week, John Huber from the Canadian Department of Natural Resources and John S. Noyes from the Canadian National Collection of Insects have announced the discovery of a new species of fairyfly, which they named Tinkerbella nana, after the fairy and the dog from Peter Pan. Happily, 'Nana' happens to be derived from 'nanos', the Greek word for 'dwarf'.

A member of the family Mymaridae, which includes the smallest known insects in the world, T. nana stretches to just under 250 μm (micrometres), which is so impossibly small, it's just 111 μm larger than the current smallest insect in the world - a male Dicopomorpha echmepterygis Mockford, found in 1997 and stretching a mere 139 μm long.

The Tinkerbella fairyflies were collected using a super-finely knit net that was swept through rainforest vegetation at the La Selva Biological Station in the province of Heredia, Costa Rica, over two hour periods, and then dumped into ethanol to preserve the catch.

Publishing their findings in the current issue of Journal of Hymenoptera Research, the Huber and Noyes describe the species' pale colouring, ranging from yellows and browns and white, and spectacular wings, covered in delicate, long bristles called macrochaeta. They suggest that this type of wing could help the fairyfly to reduce the levels of drag and turbulence it has to fight while in the air, which is important, seeing as they have to flap their tiny wings hundreds of times per second just to keep afloat.

While distinct in enough ways to earn itself a place in a new genus, T. nana is closely related to the world's smallest known winged insect, Kikiki huna, which has a body length of just 155 μm. Huber and Noyes say this is probably about as small as a winged insect could possibly get, however Huber remarked, "If we have not already found them, we must surely be close to discovering the smallest insects and other arthropods."

Papers cited:

Norman F. Johnson (1995). Variation in Male Genitalia of Merope tuber Newman (Mecoptera: Meropeidae) Journal of the Kansas Entomological Society, 68 (2), 224-233

Louis A. Somma, James C. Dunford (2007). Etymology of the earwigfly, Merope tuber Newman (Mecoptera: Meropeidae): Simply dull or just inscrutable? Insecta Mundi

Machado, R., Kawada, R., & Rafael, J. (2013). New continental record and new species of Austromerope (Mecoptera, Meropeidae) from Brazil ZooKeys, 269, 51-65 DOI: 10.3897/zookeys.269.4255

Huber, J., & Noyes, J. (2013). A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods Journal of Hymenoptera Research, 32, 17-44 DOI: 10.3897/jhr.32.4663

****