Order Mecoptera - Scorpion Flies

• Common Scorpion Fly
• Winter Scorpion Fly

Soft-bodied insects in which the head is prolonged downwards into a beak with the biting jaws at the lower end. The head bears long, thread-like antennae and large eyes. Two similar pairs of wings are usually present, but a few species are wingless or have atrophied wings. Both sexes have tiny cerci at the tip of the abdomen. The male abdomen is frequently turned upwards and swollen, reminiscent of the tail and sting of a scorpion - hence the common name of the group. Despite their name and appearance, however, the insects are quite harmless. Metamorphosis is complex, with up to seven larval stages and a pupal stage. The larvae resemble caterpillars in general appearance. This is a small Order with only about 300 species, but like the Neuroptera, it is an ancient group. In fact the oldest known fossil endopterygotes - about 250 million years old - are Mecoptera and it is believed that the butterflies and moths, caddis flies, fleas and true flies all evolved from mecopteran-like ancestors. Some of the present-day Australian Scorpion Flies appear to have survived with little change since Permian times and qualify as 'living fossils'. Four species occur in Britain.

Description. Adult fully winged, about 15 mm long. Body dark brown; wings with dark brown or black spots and blotches. Terminal segments of the male abdomen considerably swollen and carried scorpion-fashion above the body. Larva caterpillar-like, up to 20 mm long, with three pairs of thoracic (true) legs and eight pairs of fleshy, abdominal prolegs.

Biology. Although fully winged, the adults rarely fly very far and spend much of their time crawling on vegetation in damp, shaded places near water and along hedgerows. They are largely carnivorous, sometimes eating aphids and other small soft-bodied insects, but often they seem reluctant to attack living prey and feed mainly on injured or dead insects and other carrion. They sometimes steal food from spiders' webs and will occasionally nibble over-ripe fruit. There is one generation a year. Eggs are laid in soil and the larvae live as scavengers in the soil and leaf litter, where eventually they also pupate.

Distribution. British Isles and Europe.

Photo: V.J. Stanek ©
Illustration: modified from Miyake 1912 (Tokyo J. Coll. Agric. 4, 117-139)

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Adult male

Larva

Description. Adult flightless, usually under 3mm long, and dark glossy brown in colour. Wings reduced to two pairs of bristle-like structures in the male and to one pair of scale-like structures in the female. Female has a prominent ovipositor at the end of the abdomen and resembles a minute cricket. Larva grub-like with the body curled into a coma-shape (rather like a tiny chafer grub). There are no abdominal prolegs as found in Panorpa species (see above).

Biology. Adults appear in autumn and winter. They are most often seen when snow is on the ground. This feature and their jumping ability, is responsible for the common name of 'Snow Flea'. Both adults and larvae feed on mosses. When full grown, the larvae pupate among mosses or in the soil just below.

Distribution. British Isles and Europe.

Photo: V.J. Stanek ©
Illustration: modified from Withycombe 1922 (Trans. ent. Soc. Lond. 1921, 312-318)

Adult female, with long ovipositor

Adult male