(plural Uropygi, also known as Thelyphonida)

A uropygid, commonly known as a "whip scorpion", "vinegarone", or "vinegaroon", is an invertebrate animal belonging to the order Uropygi in the class Arachnida, in the subphylum Chelicerata of the phylum Arthropoda.

Physical description

The name "uropygid" means "tail rump", referring to the whip-like telson on the end of the pygidium, a small plate made up of the last three segments of the abdominal exoskeleton.

Whip scorpions range from 25 to 70mm in length; the largest species, Magistoproctus, can reach 85mm.

Like the related orders Schizomida, Amblypygi, and Solpugida, the uropygids 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. Whip scorpions have no poison glands, but they do have glands near the rear of their abdomen that can spray a combination of formic and acetic acid when they are bothered. The acetic acid gives this spray a vinegar-like smell, giving rise to the common name "vinegarone".

Behavior

Whip scorpions are carnivorous, nocturnal hunters feeding mostly on other insects but sometimes on worms and slugs. 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 whip scorpions, and leave the burrow; the mother dies soon after. The young grow slowly, going through three molts in about three years before reaching adulthood.

Habitat

Uropygids are found in tropical and subtropical areas worldwide, usually in underground burrows which they dig with their pedipalps. They may also burrow under logs, rotting wood, rocks, and other natural debris. They enjoy humid, dark places and avoid the light.

Families of uropygids include:

• Geralinuridae
• Hypoctonidae - Malaya
• Thelyphonidae - Pacific
• Typopeltidae - Indochina

As of 2000, over 100 species of uropygids have been described worldwide.