Who is eating the radishes?!

Took a photo of these guys. I was hoping to have some greens for the hens, but hungry caterpillars got them instead. So I've been feeding the caterpillars to the hens, but apparently not fast enough! What are they, aside from a bleak reminder that I have forgotten almost everything I read about insects over the last couple of years. :( I figured it would happen... with a third of an acre of grass, weeds, trees, shrubs, flowers, vegetables, chickens and bird baths--bugs just don't attract my attention they way they did when I lived alone in the heart of the city with a postage stamp-sized back yard, potted plants, and in ground irrigation. Here in the north valley, the good news and the bad news is that there is so darned much to ponder!