Order MECOPTERA (Scorpionflies) and their relatives
Boreus californicus female, photo by Baldo Villegas (Fig. 17)


Mecoptera: from the Greek mekos = length, and ptera = wings. The wings of most mecopterans are long and rather narrow.

Mecopterans are small to large insects; boreids can be as small as 2 mm long and some bittacids are over 25 mm long with wingspans of over 50 mm. The body is usually slender and soft. Most species have a distinctive, down-turned, beak-like prolongation of the front of the head with biting mouthparts at the tip. In some Nannochoristidae the mouthparts are specialized for sucking. The compound eyes are large and all families except the Meropeidae and Apteropanorpidae have ocelli. The antennae are long and threadlike, usually about half the body length, with about 16 to 60 segments. Most mecopterans are winged, but some have the wings reduced or absent. Fully winged forms have two pairs of long, rather narrow, membranous wings, with the fore and hind wings similar in size, shape and venation. The venation is generalized, characterized by numerous crossveins. Dark spots and bands occur on the wings of many panorpids and some bittacids. The legs are long and slender; the tarsi are 5-segmented, the fifth bearing two claws in all but the Bittacidae. In this family, a single, enlarged tarsal claw, along with tarsal segment 5, folds back on segment 4, forming a raptorial tarsus.

The Mecoptera is a minor insect order of about 500 described species arranged in nine families. There are about 83 species known in North America. Although small, the order is diverse and is of great evolutionary interest, because it is closely related to the stem groups of the Diptera, Siphonaptera, Trichoptera and Lepidoptera (“Panorpoid Complex”). The Mecoptera possibly contains the sister group of the Diptera. The order originated in the Permian.

There are five families in North America. The Boreidae (snow scorpionflies) is a family of small, flightless insects that are active as adults mainly in the winter. This is BC’s only mecopteran family. The Panorpidae (common scorpionflies) contains most of the species in the order -- about 300 world wide, living mainly on the northern continents. The genitalia of the male give the family its name – these structures are large, bulbous and often flexed forward over the abdomen, looking something like a scorpion’s sting. In North America, the 54 described species are placed in the mainly eastern genus Panorpa. The five species of Panorpodidae (short-faced scorpionflies) live in the southern Appalachian Mountains. Members of the Bittacidae (hangingflies) look a little like a large, four-winged crane fly (although one western US species is wingless); they hang from vegetation by their front or middle legs and capture insect prey with the hind pair. There are about 145 known species; the family is especially diverse in South America and Australia and contains the only African mecopterans. The Meropeidae are called earwigflies because the male has long, terminal abdominal appendages that resemble the pincer-like cerci of earwigs. There are only two species, one in eastern North America and the other from western Australia.

Most scorpionflies live in moist, shady habitats, especially among vegetation in broad-leaved forests, where the adults are herbivors, scavengers or predators, depending on the group. Many feed on fluids such as nectar and honeydew. They usually lay their eggs in the soil and the larvae, which are mostly caterpillar-like, feed on a wide range of dead and decomposing animal matter. The most obvious exceptions are the aquatic Nannochoristidae of South America, Australia and New Zealand, whose larvae prey on chironomid and other fly larvae; the flightless Boreidae of the Northern Hemisphere, which feed on mosses in both the larval and adult stages and whose adults are often active on snow; and the Tasmanian Apteropanorpidae, which resemble the Boreidae in form and habits. Adults and larvae of the Panorpidae are typical practitioners of the scavenging life, feeding on dead insects – often stealing prey from spider webs. Males offer an insect carcass to females as an inducement to mate; if a carcass is unavailable, a pile of saliva is used instead. Larval Bittacidae also often eat dead insects, but the adults are predators, snaring small flying prey with their hind legs while hanging from twigs or leaves.

Description of Family
Family Boreidae (Snow Scorpionflies) (Figs. 17 & 18)
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.


Penny, N.D. 1977. A systematic study of the genus Boreus (Mecoptera: Boreidae). University of Kansas Science Bulletin 51(5): 141-217.