Wednesday 18 September 2013

Three new species of Scorpionfly from the early Eocene of British Columbia and Washington State.

The Scorpionflies (Mecoptera) are a group of insects related to the True Flies. They get their name from the reproductive organs of the males of some species, which resemble the tails of Scorpions. Despite this fierce appearance most species are harmless herbivores, though it is thought that fleas are highly specialized members of the group, and the True Flies, Butterflies and Moths may have evolved from the group in the Mesozoic. The group has a fossil record dating back to the Permian, and it has been suggested that the Scorpionflies were the first Insects to pollenate plants, possibly pollenating gymnospermous plants in the Jurassic before the origin of true flowering plants.

In a paper published in the Journal of Paleontology in July 2013, Bruce Archibald of the Department of Biological Sciences at Simon Fraser University, the Museum of Comparative Zoology and the Royal British Columbia Museum, Rolf Mathewes, also of the Department of Biological Sciences at Simon Fraser University and David Greenwood of the Biology Deptartment at Brandon University, describe three new species of Scorpionfly from British Columbia, Canada, and Washington State, USA.

All three new species are deemed sufficiently different  to previously described species to be placed in a new genus, Eorpa, and family, Eorpidae. where 'Eorpa' means 'Dawn Scorpionfly' and Eorpidae derives from Eorpa.

The first new species is named Eorpa ypsipeda, where 'ypsipeda' means 'highlands'. The species is described from 21 fossil specimens, most of which comprise only individual wings or parts thereof, from the early Eocene Kamloops Group at McAbee in British Columbia and nine less certain specimens from the Klondike Mountain Formation at Republic in Washington State. These are 15.5-16.5 mm Scorpionflies. Their wings are dark with two lighter patches on each.

Eorpa ypsipeda nearly complete specimen from McAbee in British Columbia. Archibald et al. (2013).

The second new species is named Eorpa elverumi, in honour of John Elverum, who discovered the first specimen of this species, and who was actively involved in collecting at Republic. The species is described from two isolated forewings only (insect wings are considered highly distinctive and it os common to describe species based upon wings only, though not with other isolated parts of the anatomy), both collected at Republic in Washington State.

Eorpa elverumi from Republic in Washington State. Archibald et al. (2013).

The final new species is named Eorpa jurgeni, in honour of Jurgen Mathewes, brother of Rolf Mathewes and a dedicated collector of fossils. The species is described from a single hindwing, discovered at Quilchena in the Okanagan Highlands of British Columbia. 

Eorpa jurgeni from the Okanagan Highlands of British Columbia. Archibald et al. (2013).

Archibald et al. note that like other groups of Insects the Scorpionflies underwent a dramatic evolutionary radiation at the beginning of the Cenozoic, but that, unlike other insect groups, they have subsequently suffered a great loss in diversity, with four of six families present in the Eocene having subsequently gone extinct (four out of a total of fourteen Insect families across all known orders to have gone extinct in this time). They suggest that this might be for two reasons. Firstly Scorpionflies, unlike most insect groups, are largely restricted to the temperate zones, with only two genera known from the tropics, both of which are high altitude Insects, still living in a cooler climate. In the Eocene the climate was far less seasonal in the temperate zones, meaning that Insects living there then would not have been exposed to the wide variations of temperature that modern temperate zone insects have to endure. Secondly, Scorpionflies feed largely upon the bodies of dead insects; they do not actively hunt, but forage for insects which have died through other causes. One of the great success stories of the Cenozoic has been the rise of the Ants, which were an extremely minor part of the Cretaceous fauna but are now estimated to make up roughly a third of the planet's insect biomass, and actively dominate and manage many habitats. Ants compete with Scorpionflies for Insect carrion, and may be the reason that the Scorpionflies have never colonized the tropics, where the Ants are most successful.

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