Western Fence Lizard

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The fly in this photo looks a lot like a bee, but if you look at it closely, you'll see only one set of wings, the mark of a Dipteran, a member of an enormous Order of insects, all with two wings; for instance, mosquitoes are Dipterans. The name says it all, in Greek: di=two; ptera=wing. Mimicry of bees and wasps is popular among the Dipterans, and they are really good at it. Those stripes are meant to tell you to steer clear. Maybe that's why the fence lizard is hesitating.
To learn a more about bee mimicry, this is a great page: https://beespotter.org/topics/mimics/