| Vinegarroons | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Arachnida |
| Order: | Thelyphonida O. P-Cambridge, 1872 |
| Families | |
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| Diversity | |
| c. 15 genera, > 100 species | |
Thelyphonida is an arachnid order comprising invertebrates commonly known as vinegaroons (or vinegarroons). They are often called uropygids in the scientific community after the former order Uropygi (which originally also included the order Schizomida). They are also known as whip scorpions because of their resemblance to true scorpions and because of their whiplike tails.
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The name "uropygid" means "tail rump", from Greek οὐροπύγιον (ouropugion),[1] from οὐρά (oura) "tail" and πυγή (puge) "rump" referring to the whip-like flagellum on the end of the pygidium, a small plate made up of the last three segments of the abdominal exoskeleton.
Vinegarroons range from 25 to 85 mm (0.98 to 3.3 in) in length, with most species not longer than 30 mm (1.2 in); the largest species, of the genus Mastigoproctus, reaching 85 mm (3.3 in).[2]
Like the related orders Schizomida, Amblypygi, and Solifugae, the vinegarroons use only six legs for walking, having modified their first two legs to serve as antennae-like sensory organs. Many species also have very large scorpion-like pedipalps (pincers). They have one pair of eyes at the front of the cephalothorax and three on each side of the head, a pattern also found in scorpions.[2] Vinegarroons have no venom glands, but they have glands near the rear of their abdomen that can spray a combination of acetic acid and octanoic acid when they are bothered.[2] The acetic acid gives this spray a vinegar-like smell, giving rise to the common name vinegarroon.
Vinegarroons are carnivorous, nocturnal hunters feeding mostly on insects and millipedes,[2] but sometimes on worms and slugs. Mastigoproctus sometimes preys on small vertebrates.[2] The prey is crushed between special teeth on the inside of the trochanters (the second segment of the leg) of the front legs. They are valuable in controlling the population of roaches and crickets.
Males secrete a sperm sac, which is transferred to the female. Up to 35 eggs are laid in a burrow, within a mucous membrane that preserves moisture. Mothers stay with the eggs and do not eat. The white young that hatch from the eggs climb onto their mother's back and attach themselves there with special suckers. After the first molt they look like miniature vinegarroons, and leave the burrow; the mother dies soon after. The young grow slowly, going through three molts in about three years before reaching adulthood. They live for up to another four years.[2]
Vinegarroons are found in tropical and subtropical and Hot Dry areas worldwide. They are missing in Europe, Australia, and, except for an introduced species, in Africa.[2] They usually dig underground burrows with their pedipalps, to which they transport their prey.[2] They may also burrow under logs, rotting wood, rocks, and other natural debris. They prefer humid, dark places and avoid light.
As of 2006, over 100 species of vinegarroons have been described worldwide. Subtaxa of vinegarroons currently include only one extant family and a doubtful extinct family:
Rowland & Cooke (1973)[3] provided a useful synopsis of the order, including a key to genera and a checklist of species. They also presented a novel classification that included the division of the group into two families, Thelyphonidae and Hypoctonidae. Weygoldt (1979)[4] suggested the existence of two families was not supported by the available data, and Haupt & Song (1996)[5] formally reduced the Hypoctonidae to a subfamily as there was little support for a monophyletic Hypoctonidae. Dunlop & Horrocks (1996)[6] suggested that the hypoctonids may be the sister-group to the Schizomida and Proschizomus Dunlop & Horrocks 1996, but the character polarities they utilized were regarded as uncertain and many features of Proschizomus were not observable in the fossilized material.[7]
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