Saturday 14 June 2014

Robber Flies from Cretaceous amber.

Robber Flies (Asilidae) are True Flies (Diptera) noted for their aggressive predatory behaviour, which includes taking other Insects on the wing. They are stout, bristly Flies, found across the globe other than in the Antarctic, but favouring open grasslands. Robber Flies can be quite large, with most species over 1 cm in length, and the biggest exceeding 5 cm. The Group have a fossil record dating back to the Early Cretaceous, with the oldest known fossils occurring in the Crato Formation of northeastern Brazil, about 112 million years old.

In a paper published in the American Museum Novitates on 21 April 2014 Torsten Dikow of the Department of Entomology at the National Museum of Natural History and David Grimaldi of the Division of Invertebrate Zoology at the American Museum of Natural History describe two new species of Robber Flies from Cretaceous amber.

The first new species described is named Burmapogon bruckschi, where ‘Burma-’ refers to the origin of the specimens, and ‘-pogon’ means ‘beard’, a common suffix for Robber Fly genera due to their bristly nature, while ‘bruckschi’ honours Klaus-Peter Brucksch of Kuranda, Queensland, who obtained one of the specimens from which the species is described in the Hukawng Valley in Myanmar. The species is described from two specimens from Burmese amber, which originates in Kachin State in northern Myanmar, and which has been dated to 99 million years old using uranium-lead isotope methods. The male specimen is slightly smaller than the female specimen, at 6.5 mm compared to 8.0 mm. 

Male specimen of Burmapogon bruckschi in lateral view. Dikow & Grimaldi (2014).

Female specimen of Burmapogon bruckschi in lateral view. Dikow & Grimaldi (2014).

The second new species comes from Raritan amber, which occurs in the Raritan Formation that outcrops in Long Island and Staten Island as well as in central New Jersey, and which is thought to be between 90 and 94 million years old, based upon pollen data; this particular specimen coming from the White Oaks (or Old Crossman’s) Clay Pits in New Jersey. The species is described from a single specimen, assigned to the subfamily Leptogastrinae, which comprises slender Robber Flies. The species is named Cretagaster raritanensis, where ‘Creta-’ means ‘chalk’, referring to its Cretaceous origin and ‘-gaster’ means ‘stomach’, a common suffix for members of the Leptogastrinae, while ‘raritanensis’ means ‘from the Raritan’, in reference to the Raritan Formation. This is the oldest known member of the Leptogastrinae.

Cretagaster raritanensis. (A) Incomplete specimen in dorsolateral view (with enlarged structure of hypopharynx). (B) Head in anterior view. (C) Left prothoracic leg in lateral view. Dikow & Grimaldi (2014).

See also…

Winter Crane Flies (Trichoceridae) are large True Flies (Diptera) with a (slightly erroneous) reputation for being tolerant of cold conditions. In fact a few species are capable of remaining active in winter, with some even mating and laying eggs beneath snow...

Non-biting Midges (Chironomidae) are small Flies closely related to the Biting Midges, Solitary Midges and Blackflies. They closely resemble Mosquitoes, but despite their appearance and relationships...

Axymyids are medium sized, stout bodied, True Flies (Diptera) related to the Gnats, Midges, Mosquitoes and Crane Flies. They have a fossil record going beck to the Jurassic, but are rare today, with only six described species.

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