Reader Pete Johnson took this awesome photo of the red-splotched abdomen of a poisonous black widow spider. One of my favorite things about this shot: The fact that you can see hairs growing on the spider's abdomen.
Extra bonus: Until checking out this photo—and subsequently reading up a bit on black widows—I had no idea this spider came in brown. The specimen in this photo could be a male, or it could be one of several species that are simply brown widows, rather than black. Looking at the legs, there's a good chance it's Latrodectus geometricus.
Great work, Pete!