Diplura
The order Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (springtails) and Protura).[3] The name "diplura", or "two tails", refers to the characteristic pair of caudal appendages or filaments at the terminal end of the body.
Around 800 species of diplurans have been described, of which around 170 occur in North America,[4] 12 in Great Britain[5] and two in Australia.[6][7]
Diplurans are typically 2–50 millimetres (0.08–1.97 in) long, with most falling between 7 and 10 millimetres (0.28 and 0.39 in).[7] However, some species of Japyx may reach 50 mm (2.0 in).[5] They have no eyes and, apart from the darkened cerci in some species, they are unpigmented.[5] Diplurans have long antennae with 10 or more bead-like segments projecting forward from the head.[8] The abdomens of diplurans bear eversible vesicles, which seem to absorb moisture from the environment and help with the animal's water balance.[8] The body segments themselves may display several types of setae, or scales and setae.[9]
Diplurans possess a characteristic pair of cerci projecting backwards from the last of the 11 abdominal somites.[10] These cerci may be long and filamentous or short and pincer-like,[11] leading to occasional confusion with earwigs.[6] Some diplurans have the ability to shed their cerci if necessary (autotomy). Moulting occurs up to 30 times throughout the life of a dipluran, which is estimated to last up to one year.
As entognaths, the mouthparts are concealed within a small pouch by the lateral margins of the head capsule. The mandibles usually have several apical teeth.[9] Diplurans do not possess any eyes or wings.[7]
In males, glandular setae or disculi may be visible along the first abdominal sternite. External genital organs are present on the eighth abdominal segment.[9]
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