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.
Physical description
Palpigrades are tiny cousins of the uropygid, or whip scorpion, no more than 3mm 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 species have three pairs of book lungs, while others have no lungs at all.
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.
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.
The ninth somite is of more diverse character.In the Scorpions and in the other Arachnida in which the prosoma and opisthosoma are joined across their whole breadth, the somite is not present in the adults, but its temporary existence has been observed in the embryo Scorpion.
The same is true of the more primitive Spiders, but in the majority the second pair have disappeared and tracheal tubes take their place, opening at a pair of spiracles on the lower side of the opisthosoma.
In the Solifugae and the Palpigradi, there is an additional tube, the labyrinth sac, lined with secretory cells, between the saccule and the labyrinth.
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