Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
By Richard M. Baranowski. Written in 1986, this key is available in both JPEG and PDF format.

Here is a direct link to the key.

dead link :/
should be in Books, not Links: it's a printed paper [available online, too]
NB: there is a Books entry already(1)