Black Widow guarding her egg sack

Pest Status: Most notorious of all spiders in the United States; venom is highly virulent, but the spider is quite timid. Even when disturbed in its web it attempts to escape rather than to attack. Widow spiders are known from every state (except Maine where it undoubtedly also occurs) and several Canadian provinces. It is uncommon in the north but quite abundant in the south and west.

From the book:Field Guide to Texas Insects,  Drees, B.M. and John Jackman, Copyright 1999 Gulf Publishing Company,Houston, Texas
 

Hooking up to haul a classic 1954 Dodge Coronet and there she was... in the underside of the tire rim. (We left the rim for her)