I think I can safely say that Charley Harper's work is enjoying a bit of a renaissance and that most people will be looking at these images and thinking ...so that's who did those!
Harper illustrated The Golden Book of Biology (1961) and the Ford Times, and worked for the American National Park Service, Cincinnati Zoo and the Nature Centre, Hamilton County (Ohio) Park District, Hawk Mountain Sanctuary in Pennsylvania and the Everglades National Park.
He called his style "minimal realism" and said "When I look at a wildlife or nature subject, I don’t see the feathers in the wings, I just count the wings. I see exciting shapes, colour combinations, patterns, textures, fascinating behaviour and endless possibilities for making interesting pictures".