The Mecoptera are small to medium-sized insects known commonly as scorpion-flies because the males tend to curve their abdomens upwards, making them resemble a scorpion’s tail. There are about five hundred described species worldwide. The scientific name comes from the Greek and means “long wings”. The adults either resemble lacewings (Order Neuroptera) with their two pairs of transparent, heavily veined wings, or they look like craneflies (Order Diptera, Family Tipulidae) with their long legs and antennae. The wings can be held flat or folded back roofwise over the abdomen. Adults have long snouts equipped with chewing mandibles and a long, cylindrical abdomen. Scorpion-flies are often seen hanging from vegetation which gives them their other common name of hanging-flies.
Mecoptera have a complete life cycle with larval stages followed by pupation and metamorphosis into completely different adult forms. Adults hatch from their pupal cases in spring, and congregate in cool, moist habitats such as swamps or stream banks in forests. Both sexes feed on nectar, but male scorpion-flies also prey on caterpillars and soft bodied insects. They make short darting flights to catch their prey on the wing or stalk them on the vegetation. Females have only been observed feeding on nectar.
Courtship has been described as ‘complicated’. A male catches an insect, but instead of eating it, he carries it by his hind legs to a female. The female is attracted by musky smells emitted from the male and approaches. He grabs and holds her with his legs, at which point things get a bit agitated. The male puts his abdomen against hers and copulation begins. To calm her during this process, he feeds her the insect, or, in some species, he feeds her fluids from his mouth. He can then let go until copulation finishes, when they separate and she flies off. He finishes off the remainder of the meal, cleans his legs and flies off in search of more prey and another female. She may be mated by several males in a row, but she is only attracted to males who have a food offering. Because she only feeds on nectar, she needs this protein meal to produce eggs.
The female lays the eggs either singly or in clusters in moist hollows in the soil. Scorpion-flies can produce two generations in a summer. The autumn adults are usually bigger and darker than those hatched in the spring. Most of the caterpillar-like larvae are terrestrial and can either be herbivorous or carnivorous. A few produce aquatic larvae that are long, thin and resemble wire-worms.
Scorpion-flies are part of the food chain, preying on other insects and in turn serving as a food source for birds and other higher predators. Other than this, scorpion-flies have no economic benefit to humans. For this reason they are not a well studied group of insects.
Information sources: Britten etal 1979 Insects of Australia chapter 32 Mecoptera by E. F. Reik CSIRO