Somtimes mistaken for scorpion
s, solpugids also inhabit the Sonora desert
in great numbers. They can often be seen outdoors at night crawling up wall
s and scuttling over rock
s and branch
es. Solpugids are yet another reason (besides scorpion
s, etc) that I'm glad I'm not a beetle
Solpugids are also called "sun spiders" -- they are arachnids, but that's where the resemblance to spiders ends. The major distinguishing feature of the solpugid, I have found, is that they never, ever seem to stop moving. It would be hard to tell a running scorpion and a running solpugid apart, but scorpions are usually fairly sluggish, so anything running that fast is probably a solpugid. If you can get it to stay still, you will notice that it has two large, thick pedipalps out in front, like an oversized pair of legs.
Solpugids are voracious predators -- I've never seen one eat, but the encyclopedia says they consume more per day than any other arachnid, period. The appearance of a solpugid is difficult to describe, so you should find a photo in a book or on the network to make a positive identification. They're light yellow-brown, with a darker thorax, and are a little bit larger than your average bark scorpion. I have seen solpugids that were as large as a US half-dollar, however. Though they look very fearsome, they do not carry any venom. They also prey upon certain small vertebrates, like small lizards. This means that they carry a vicious bite and are probably capable of dismembering their meals, so don't pick them up.
Don't kill solpugids. They eat up all the bad bugs. If there is a solpugid in your house, put him back outside, or take care of your infestation problem -- solpugids won't stay in if there's nothing to eat.