i have an invasion of beetles
& they are eating only one kind of plant on the riverbank
i posted a request for an id of the beetle on the garden foe forum http://davesgarden.com/forums/t/596603/
maybe an identification of the plant would help figure out what is going on
here is a pict of the plant they are targeting & one of the beetles
The leaves look a little bit like Toyon (Heteromeles arbutifolia), althought it probably looks like a lot of other things as well, that's just something I had in my garden that it reminded me of. Does it have white flowers in summer and red berries in fall/winter? If it is Toyon, the bug that causes chewed leaves (according to Pests of Landscape Trees & Shrubs) is the Fuller Rose Beetle. There's no photo of the beetle in the book, but the shape of it in the illustration looks similar to the one in your photo. And it only preys on certain plants, generally ones in the rose family, so that would explain why it's not bothering your other plants.