im no help, but mine are the same way. i just replanted with the plants really close together so hopefully the bugs will only get a couple of the plants. i have yet to find anything on the plants actually eating them....ive looked at all times of day and night. its really confusing.

Could it be slugs? I spotted a big one looking interested in my beans the other day, so I sprinkled Sluggo around. Other pests that are known to attack beans are Mexican Bean Beetles and the ever-popular Japanese Beetle.

Lacy pattern is made by Japanese beetles. They are major pests, and just really nasty.