FAMILIES OF MECOPTERA OF British Columbia

by

R. A. Cannings and G. G. E. Scudder 

Copyright © 2005 - All rights reserved

Description of Family Boreidae (Snow Scorpionflies)

Boreids range from yellow and rust to brown and black in colour and from about 2 to 7.5 mm in length. The body is usually clothed in a variety of short hairs, bristles and denticles. The head is prolonged into a rostrum composed anteriorly of the clypeus and labrum, laterally of the genae and posteriorly of the maxillae and labium. The mandibles are slightly longer than the short labrum and taper, bearing six teeth near the tip; the maxillary palps are 5-segmented. In life the large, oval eyes are purple to black; there are three ocelli. The threadlike antennae are 18 to 25-segmented; the two basal segments are thickened. The pronotum is saddle shaped and often has bristles on the front and back margins. The mesoscutellum frequently bears two crossed bristles. The legs have large, conical coxae, long femora and tibiae and slender, 5-segmented tarsi bearing two claws. The front wings of the female are reduced to flaps covering smaller hind wings, which are reduced to small, irregular folds. The male’s wings are modified as thin hooks. The front pair extend to about abdominal segment 4 and bear spines on the inner and outer margins; they cover the hind wings, which are thin and cylindrical. The female abdomen consists of 11 segments -- the sternum of 8 is elongate, forming the lower part of the ovipositor. The terga of segments 9 and 10 form the top of the ovipositor and segment 11 and the cerci fuse to form the short triangular tip. The cerci are fused in Boreus but incompletely joined in Hesperoboreus. The male’s sternum 9 is elongate triangular and sometimes deeply notched.

Snow scorpionflies live mainly in mosses, especially those that are low, compact and matted. Larvae eat mosses and adults do also, although there is speculation that the latter may also feed on springtails. Caurinus dectes Russell feeds on liverworts. In most areas, adults are found from November to April, although at high altitudes and latitudes adult emergence may occur later. For example, Boreus borealis Banks, living on the Pribilof Islands in the Bering Sea, has been collected only from May through August. In BC, Boreus specimens are usually collected on snow when the temperature is at, or slightly above, above 0ºC. Their dark colour may help them absorb heat. Especially when the snow is soft or if they are disturbed, individuals will hop, using their long hind legs, and often land, legs tight to their body, looking like nothing more than a bit of detritus. There can be considerable activity on sunny, warm days, but evidently most mating and dispersal occurs in still, cloudy weather.

The Family Boreidae consists of small scorpionflies so distinctive that they are sometimes placed in their own suborder, or even order – the Neomecoptera. It is a small holarctic family of 28 described species divided into three genera. Boreus contains 26 species – 14 in Eurasia and 12 in North America. Two species of Hesperoboreus live in western North America from Washington to California and Caurinus dectes is known only from Oregon. Two of the Nearctic species of Boreus are eastern and 10 are western; six of the latter occur in BC. Perhaps the most striking is B. elegans Carpenter, which inhabits low elevations on the south coast of BC and in western Washington. The largest species in the family (big females can reach almost 8 mm in length) and a rusty red colour, it is the symbol of the Entomological Society of British Columbia. Also strictly coastal is B. insulanus Blades, known only from southern Vancouver Island. The most widespread species in the province, B. californicus Packard, ranges from the Yukon and northern BC south to Arizona and California. Boreus nix Carpenter, B. pilosus Carpenter and B. reductus Carpenter also are recorded in the province.