Quote from en.wikipedia.org/wiki/Thelypho…
Thelyphonida is an arachnid order comprising invertebrates commonly known as vinegaroons (also spelled vinegarroons and vinegarones). 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 tail.
The name "uropygid" means "tail rump", from Greek οὐροπύγιον (ouropugion), 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.
Whip scorpions range from 25 to 85 mm (1.0 to 3.3 in) in length, with most species having a body no longer than 30 mm (1.2 in); the largest species, of the genus Mastigoproctus, reaching 85 mm (3.3 in). Because of their legs, claws, and "whip", though, they can appear much larger.
Like the related orders Schizomida, Amblypygi, and Solifugae, the vinegaroons use only six legs for walking, having modified their first two legs to serve as antennae-like sensory organs. All species also have very large scorpion-like pedipalps (pincers) but there is an additional large spine on each palpal tibia. 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. Vinegaroons 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. The acetic acid gives this spray a vinegar-like smell, giving rise to the common name vinegaroon.
Vinegaroons are carnivorous, nocturnal hunters feeding mostly on insects, millipedes, scorpions, and terrestrial isopods  but sometimes on worms and slugs. Mastigoproctus sometimes preys on small vertebrates. The prey is crushed between special teeth on the inside of the trochanters (the second segment of the "legs") of the front appendages. They are valuable in controlling the population of roaches and crickets.
Males secrete a spermatophore, which is transferred to the female. After a few months the female will dig a large burrow and seal herself inside. Up to 40 eggs are extruded, within a membranous broodsac that preserves moisture and remains attached to the genital operculum and the fifth segment of the mother's ventral opisthosoma. The female refuses to eat and holds her opisthosoma in an upward arch so the broodsac does not touch the ground for the next few months as the eggs develop into postembryos. Appendages become visible The white young that hatch from the postembryos, climb onto their mother's back and attach themselves there with special suckers. After the first molt, they look like miniature adults but with bright red palps, and leave the burrow. The mother may live up to two more years. The young grow slowly, going through four molts in about four years before reaching adulthood. They live for up to another four years.