Scorpionflies (Order: Mecoptera)
A photograph of a female scorpionfly (Panorpa panorpa). Females do not possess the characteristic scorpion sting-like genitalia that gives scorpionflies their name.
This is an interesting group of insects, with around 300 species. Around 30 of these are found in Europe, but no more than half a dozen or so in the UK.
The head of a scorpionfly is shaped like a beak, and this is a feature that is useful in distinguishing them from other insects.
There are three main groups of scorpionflies:
Common scorpionflies (Panorpidae). This is the largest family, and it is only this family that has the upturned scorpion-like genitalia or 'tail' that gives the order its name. They are brownish yellow and black insects with mottled wings and are found among shaded vegetation and in hedgerows.
They feed on dead or dying insects (including any they might spot in a spider's web) and are also partial to ripe fruit and, when it's available, human sweat.
The adults look somewhat scary but are in fact quite harmless. Common scorpionfly larvae mostly live in soil and look like caterpillars, having eight pairs of feet and sometimes spines.
Panorpid males attract females by vibrating their wings, and may let them feed on their saliva while mating.
Snow scorpionflies (Boreidae). These are dark brown or bronze or black in colour, with long antennae, but their wings are much reduced and hardly noticeable. They live on the surface of snow or among mosses, amongst mountains or in cold regions.
Males approach females whilst waving their antennae or wings, and then jump on them, hanging on for up to 12 hours. The males nonchalantly feed and move about during mating, while the females are passive and do not move.
Hanging flies (Bittacidae). These have long wings and legs and look like crane flies (daddy long legs) but you can tell they're not on closer examination, because they have the tell-tale beak-shaped head, and four wings (crane flies belong to the Diptera, or true flies, and have two wings and a pair of balancers or halteres).
Hanging flies hang around on bushes waiting for their prey (small insects) to come along, and use their clawed hind legs to catch them - the only insect to use this method. The caterpillar-like larvae have hairy warts and camouflage themselves by sticking leaves on their bodies.
Male hanging flies attract females with pheromones and offer them captured prey as nuptial gifts before mating. There is competition for females, and other males might try and steal nuptial gifts or, if they don't have any of their own, they might try to force a female to mate without such a gift. The really clever males mimic females in order to get a free meal!
The name of the order is derived from the Greek meco meaning long and pteron meaning wing, referring to the shape of both the front and hind wings in most species.
In evolutionary terms, this is an old group. It shows complete metamorphosis (egg, larva, pupa and adult stages) and may be the forerunner of other insects that have complete metamorphosis (butterflies, moths, caddis flies, true flies and fleas).
There are nine families of Mecoptera in all, though some of these are extinct and only described as fossils.
How to find them
For hanging flies or common scorpionflies, using a beating tray or sweep net among low shaded bushes between May and August may be effective. In the case of the snow scorpionflies, however, autumn and winter is the time to search for these. But unless you're collecting them for study, leave them untouched as snow scorpionflies can die just by being exposed to the warmth of the human hand.
Related links: Scorpionflies (Order: Mecoptera)
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