I think it's a Japanese beetle but not positive. They are making Swiss cheese out of my bean plants. What should I do?
All you have to do is type Japanese Beetle into google...press search....then press Images....and you will be able to see for yourself in about 5 seconds that that is a Japanese Beetle.
Unless you have two or three hundred feet of bean rows, you could spray with insecticidal soap....then follow afterwards with a bucket with a little soapy water in it to toss the still squirming culprits in.
These beetles don't stay on the scene for very long, thankfully.
Japanese Beetles feed on many plants and if the numbers are fairly low the simplest means of control is to go out early in the morning, before they warm up enough to fly away, and knock them off the plant into a bucket of soapy water (the soap keeps them from flying out of the bucket).
I have not found Insecticidal Soap to be very effective as a control for these buggers, but Neem Oil products and pyrethrin based sprays do when used with due care since they are vey broad spectrum poisons that will also kill off beneficial insects.
I have seen reports that indicate these Japanese Beetles are devloping immunity to Carbaryl and Malathion due to over exposure, genetic modification.
Here is a link that might be useful: About Japanese Beetles
Good advice from kimmsr, but I will add that neem doesn't work well to kill the beetles directly. It IS pretty effective as an anti-feedant /growth regulator.
Another product very helpful as an anti-feedant is 'Surround ', a special kaolin clay spray used to protect plants against some insect species, as well as heat and sun damage.