I swear these guys are like having a frat party in my backyard. I often find them in groups of three, procreating to beat the band. I've even caught them 'doing it' through a hole in a leaf, while doing it with one on the same side of the leaf. They are natures perverts! YUCK!!!
EDIT: I have video of a bunch of them on a leaf. Oh, and one 'mounting' another, and appearing to be 'thrusting' on it. I mean, OMG, it's pretty sick... #BugPorn?
I catch as many of them as I can in a bottle filled half full of a dish soap and water mix. No way is anything going to be having that much sex in MY yard!!!
EDIT THE EDIT: And they eat my roses. One year, the first year I ever saw them, they striped my many rose bushes and several ornamental trees. I mean, striped them to branches and the thick parts of the leaves. They did it completely three years in a row. Decimated rose bushes, and all. I started catching them, and spreading a variety of 'organic' grub control measures, and now I've only caught a pair on my rose bushes. One thing that made their infestation hard to end was, I believe, the rocks I had surrounding the area. I have found hundreds of grubs in the dirt that accumulates in the rock beds. Cleaning the rocks was nothing I thought I'd have to do, but all of it together seems to be working. I used to use Starbucks Iced Coffee bottles for catching/killing them, and in the worst of it would have a bottle half full of drowned beetles. I could half fill a Nestea tea bottle in one day. I had to switch to larger bottles to serve as 'kill jars' because the smaller bottles were filling up so fast. I'd see over a dozen on one leaf. I also got into a brief argument with a Japanese beetle 'expert' who said their eyesight was 'poor'. I could hear them dropping off the leaves as soon as I got within 10 feet of the areas I harvested the damn things. They have really pretty good eyesight, but fly like they are drunk. And aren't exactly intelligent. One beetle, I tried to capture, and he flew away, only to land on the same leaf, and then flew away again, and, you guessed it, landed on the same leaf. Then I got it, it actually flew into the bottle. They supposedly were imported on some agricultural items from Japan (trees).