This gentleman, who was lurking in the garden the other day, is a praying mantis. Specifically, he is, I think, a European Mantis, Mantis religiosa. This is an introduced species from Europe that has become naturalized over much of the U.S. Our native California mantis is much smaller.
I say “he.” This guy can be identified as a male because he has seven abdomen segments, as opposed to the female’s five, and he has stout, long antennae, as opposed to the wispy version sported by the female.
Mantises are formidable and not very discriminating predators. Gardeners argue whether they are beneficial, but it just depends. They’ll eat what they can catch. If you have a lot of nasty gnats and mosquitoes, they’ll eat those, and welcome to them. But if those are in short supply mantises don’t mind feasting on butterflies or even an occasional small hummingbird.