The Mecoptera is a minor insect order, with about 500 known species. Nine families are recognised and five of them occur in Australia. Two families, Panorpidae and Bittacidae, include most of the known species.
Larval Mecoptera are relatively poorly known in Australia, but terrestrial and freshwater aquatic taxa have been described. The Nannochoristidae, with several species of
, are aquatic within temperate streams. Bittacidae and Choristidae occur on the ground within leaf-litter, and Apteropanorpidae apparently occur within moss in Tasmania.
The Panorpidae are commonly called scorpion-flies because the bulbous, male genital segment often curves anterodorsally like a scorpion's sting. The family includes some 300 species in three genera and occurs in the northern continents and Indonesia but not in Australia.
The Bittacidae are sometimes known as hanging-flies because species hang from plants by the fore legs and sometimes the mid legs. The family includes about 145 species in 17 genera. Bittacids are widespread in temperate and tropical regions, being particularly diverse in Australia and South America and comprising the entire mecopteran fauna of Africa.
Kaltenbach (1978) has provided the most recent summary of the taxonomy, morphology, physiology and behaviour of the order. Byers and Thornhill (1983) reviewed the biology.
Holometabola with head usually produced as hypognathous rostrum; first abdominal tergum fused to metanotum; usually with 2 pairs of wings, these membranous, subequal in size, with complete venation.
The Mecoptera are an unusual insect order, whose affinities remain somewhat uncertain. Larvae are unique among the Holometabola in possessing true compound eyes with ommatidia, and the eruciform habit of many is reminiscent of the Lepidoptera.