| Somtimes mistaken for scorpions, solpugids also inhabit the Sonora desert in great numbers. They can often be seen outdoors at night crawling up walls and scuttling over rocks and branches. Solpugids are yet another reason (besides scorpions, birds, tarantulas, 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. | 
