WHIP SCORPIONS

Jason Dunlop

In response to Andrew Smith's request for non-spider articles, here's an introduction to a group of tropical arachnids, known as vinegaroones, or more commonly, whip scorpions. Now for a start whip scorpions are not true scorpions. They do not have a sting. They belong in the arachnid order Uropygi, although some people also class a group of very tiny arachnids called schizomids which look like smaller, blind versions of these animals with divided carapaces and stumpy tails, as whip scorpions too.

Whip scorpions are actually closely related to spiders, although you'd hardly think so to look at them. However, like tarantulas and other primitive spiders, they have two pairs of book lungs (scorpions have four pairs) and similar, fanged chelicerae (scorpion chelicerae are like little claws). Their bite is not venomous and their tail is probably a sensory device more than anything in whip scorpions.

The worst they can do is fire a jet of vinegar-like acid (hence the name vinegaroone) backwards from a pair of glands at the base of the tail. This pungent blast is designed to put off predators. They can also do what is called aggressive posturing, raising up their abdomens to make themselves look like a more dangerous animal, a venomous scorpion, which again frightens off predators. Devil's coach horse beetles mimic scorpions for protection in a similar way.

Whereas the first pair of walking legs in spiders are, well, leg-like, in whip scorpions they are long and thin and actually work more like insects' antennae, being used to probe the area ahead of the animal and search for prey by touch. Their eyes are quite small and so touch and vibration senses are probably more important. Similarly, spider palps look like little legs, but whip scorpion palps are massive and claw-like. These are, not surprisingly, used in prey capture to grasp hold of prey detected by the long legs which is then broken up and chewed with the chelicerae.

Normally they are very slow moving and seem to tentatively feel out the area ahead with their 'antenniform' legs before moving. They can scuttle quite fast though when they need to.

When they walk they don't use the long first legs and rely on the back three pairs of legs only. In this respect they are hexapodous (literally: hexa-six podous-legged) and walk like insects. They mate with a scorpion-like mating dance before the male deposits a spermatophore on the ground which the female then picks up. In some species the male, which tends to have longer palps, then inserts the tip of his palp into her genital opening and breaks it open to release the sperm.

Whip scorpions make excellent pets. I currently have an adult and a number of juveniles of the giant Texas whip scorpion, Mastigoproctus giganteus. They are easy and safe to handle, their worst claws being unable to grasp round a finger, and their worst excess is a spray of acid at an offending hand. They seem to be quite hardy and tolerant of cool temperatures. They live happily on vermiculite in which they will burrow if given the opportunity, but a log or other shelter for them to crawl under is quite adequate. The adult Texan species feeds on crickets and other small insects, but does not readily take larger prey. Juveniles on the other hand are voracious predators on micro-crickets.

Finally, whip scorpions have been with us for quite some time. There are actually British fossil whip scorpions from Coseley near Birmingham, and also from North America, Germany and the Czech Republic, all of which come from great coal swamps of the Carboniferous age. These fossils are so similar to living whip scorpions that they are all placed in the same family, Thelyphonidae. Whip scorpions are therefore rather primitive animals and could be classed as 'living fossils', having changed little since they first appeared over 300 million years ago.

Last Updated: April 04, 2007