Mystery Bean Bug

One of the things I've enjoyed about paying closer attention to my garden this year is the wide variety of new bugs I've encountered. It's amazing what you can find when you're really looking. Yesterday I came across this pretty little bug as I watered the green bean bed. The bed is mulched with rice straw and as the water flooded underneath the mulch, this guy came crawling out.

Mystery bug in the bean bed

He was about 1/2 a centimeter long, or half the size of my thumbnail. I wouldn't have noticed him, except that his bright green color stood out starkly against the yellow straw. There were two of them, actually, and I expect I'd find more hanging out under there if I pull back the mulch.

I've never seen anything like this bug in the yard before. At first I thought maybe it was the one causing the little, round holes in my bean pods, but a little bit of research on the What's That Bug? website tells me this might be some kind of treehopper, in the Membracidae family. Treehoppers damage plants by sucking their juices and making slits in bark in order to lay their eggs, not by chewing perfectly round holes out of pods. In any case, a pest.

Treehopper?

My guy looks a lot like a Buffalo Treehopper--pictures here and here--but those seem to have little horns on the top where this guy does not. The Buffalo Treehopper on the UC IPM site doesn't have horns, but looks much darker and also larger. Mine also looks like the one pictured here and labeled Atymna helena, but my guy's "helmet" seems more pronounced.

In spite of the resemblance, two things cause me to seriously question the treehopper idea. For one thing, the one that emerged from my straw mulch didn't hop. He happily climbed onto the stick you see him sitting on in the photos, and just sat there for a picture as long as I kept the stick out of the bright sunlight. Maybe he was just waterlogged and not ready to hop around.

Perhaps more importantly, though, he wasn't in a tree. Treehoppers are supposedly tree-dwelling bugs that feed on trees and don't often descend to the ground. So, I'm still not sure exactly what this is and am going to do a bit more research. Thoughts? Ever seen one in your yard?