Palpigradi
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80 species in 4 genera |
A palpigrade, commonly known as a microwhip scorpion, is an invertebrate animal belonging to the order Palpigradi in the class Arachnida, in the subphylum Chelicerata of the phylum Arthropoda.
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[edit] Physical description
Palpigrades are tiny cousins of the uropygid, or whip scorpion, no more than 3 mm in length. They have a thin, pale, segmented carapace which terminates in a whip-like flagellum, made up of 15 segments. The carapace is divided into two plates between the third and fourth leg set. They have no eyes. Some palpigrades have three pairs of abdominal lung-sacs, althought these are not book lungs as there is no trace of the characterstic leaflike lamellae which defines book lungs, while other species have no resporatory organs at all and breaths directly through the cuticle.
[edit] Behavior
As of 2003, very little is known about palpigrade behavior. They are believed to be predators like their larger relatives, feeding on minuscule insects in their habitat. Their mating habits are unknown, except that they lay only a few relatively large eggs at a time.
[edit] Habitat
Microwhip scorpions need a damp environment to survive, and they always hide from light, so they are commonly found in the moist earth under buried stones and rocks. They can be found on every continent, except in arctic and antarctic regions.
As of 2000, approximately 80 species of palpigrades have been described worldwide, all in the family Eukoeneniidae, which contains 4 genera.
[edit] Fossil record
A single fossil palpigrade species has been described from the ?Pliocene Onyx Marble of Arizona, USA. Its familial position is uncertain. Older publications refer to a fossil palpigrade from the Jurassic of the Solnhofen limestone in Germany, but this has now been shown to be a misidentified fossil insect.
