by M E Skeel

Created on: July 12, 2011   Last Updated: July 15, 2011

Strepsiptera: a strange word for a strange group of animals. The title identifies them as a kind of insect so they must have six jointed legs. What does the name mean? First, it defines the taxonomic status of the animals it names. It is an order in the Class Insecta which is a class in the Phylum Arthropoda. All arthropods have an exoskeleton with jointed legs. Insects are the class of arthropods with six jointed legs, which distinguishes them from the multi-legged millipedes and centipedes and from the eight-legged spiders and mites. The Class Insecta is large, diverse, prolific and hugely successful. The common orders include the beetles (Coleoptera or 'hard-wings'), butterflies and moths (Lepidoptera or 'scaly-wings'), ants, bees, wasps (Hymenoptera or 'clear-wing') and of course, the ever-present flies (Diptera, meaning 'two wings'). These four orders represent the vast majority of insects on Earth, but there are another twenty-seven known and described orders of insects, and the Strepsiptera is one.  The reader probably noticed that the four big Insect orders all had names ending in -ptera, the Greek word for wings. As in those orders, the first part of this order's name,  "strep", means something about their wings, in this case 'twisted'. Strepsiptera are parasites that spend most of their lives living in insect hosts such as bees and ants. About 600 species have been described. 

Strepisterans have full life cycles that involve a metamorphosis in a pupal case from larva to mature adult. The female is worm-like, with no legs or wings.  When she makes her puparium, the head end sticks out of the host and exudes a pheromone to attract the male.  When he finds her, he uses his wasp-like style to penetrate the brood sac covering that lies between her head and thorax. This is called hypodermic insemination. The eggs hatch into larvae within the brood sac. One female can produce hundreds of larvae, all with tiny legs that they use to crawl out into the wider world where they seek new host insects to infect. The larvae can be carried by the female host to her eggs and larve or they can crawl until they find the nymph of the host species. In either case, they find their way inside between the plates of the host's protective exoskeleton. Then they feed on

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