Our BugGuide group from the 2013 AZ gathering ran into two herpers around noon at a canyon wash along the Montosa Cyn/Hopkins Peak Rd. They showed us some neat things, among them a giant desert centipede:



and a tiger rattlesnake (Crotalus tigris):



Can you make out the eyes in the photos taken by Ed and I? (Ed's is the 2nd thumb above...and the full-size version of my photo is here.) I find it curious that the eyes are so cryptic in those two photos, while they're clearly visible in Patrick's and Robyn's (3rd and 4th thumbs above).

General info on this species can be found on this "Reptiles of Arizona" web page; more photos and a range map appear here; and a technical article asserting that Crotalus tigris has the deadliest venom of any nearctic rattlesnake appears here.