Diplura are primitive, wingless insects called bristletails. Like all insects, they have six legs (hexapods) and three body parts: head, thorax and abdomen. The head is eyeless but has simple antennae. In some species the antennae can be withdrawn and then telescoped out. The six legs are attached to the thorax as in all insects and the abdomen has ten segments, with a pair of cerci on the last segment. These paired, pointed cerci cause the diplurans to resemble earwigs but earwigs are more advanced insects and the resemblance is only superficial. There are hairs on the body called chaetae. All diplurans have simple chewing mouthparts that are held in a pouch and extended when eating (entognathous mouthparts).
The diplura are one of four groups of insects that are wingless throughout their lives. Other insects lose their wings secondarily but wings never develop at all in the Apterygota (protura, diplura, thysanura and collembola). For this reason, the Apterygotes are considered to be the most primitive of the living insects, their ancestors having evolved before wings.
Most diplurans are small and colourless, white or pale yellow. There are about thee hundred species described and grouped into nine families. The Japygidae are carnivorous and have well developed, pincer-like cerci which they use to catch their prey, usually other insects. The Projapygidae have simpler cerci and are herbivorous. They are unusual in that their cerci contain silk glands, much like spiders.
Most bristletails are found in moist soils and most are small, less than five millimetres in length. Some of the carnivorous forms get much larger, up to about 50 mm long. They can also be found in mosses, under the bark of trees and some species live in ant or termite nests, while others are cave dwellers. As well as eating plants, most species also are saprovores, consuming dead organic matter as well.
Like all soil animals, bristletails have predators. Most bristletails are good burrowers and the predatory forms can run quickly as well. The cerci can be dropped when grabbed by a predator, allowing the dipluran to escape. Some forms with pincers have been observed to use them in defence as well as to capture prey.
Diplurans practice indirect fertilisation. The males deposit spermatophores in the soil and females with mature eggs pick them up to fertilise the eggs. The eggs are laid in small clusters and sometimes the female protects them by wrapping her body around them. The first two instars are immobile. On the third moult, a miniature version of the adult emerges. Bristletails continue to moult and grow over their entire lives, which is usually 1-2 years long.
Because they are small and inconspicuous, not much else is known about the Diplura. They are not pests and have no economic value. Their conservation status is unknown, although some species have restricted ranges and could be adversely affected by human activities.
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