The bumps actually have great names such as maple bladder gall, roly-poly gall on oak, succulent oak gall and hackberry nipple gall. Some of the bumps like the ones on maples are bright red and pretty in a weird sort of way.
Galls are growths on leaves, stems and twigs of many different plants.
Galls can be created by insects, mites, bacteria, fungi and nematodes. The ones most often brought into our office are caused by insects and mites. There are at least 1,441 species of insects and mites that cause galls in North America. Galls are actually created by the plants themselves in response to feeding or egg-laying by certain species of insects and mites. As gall-making insects feed or lay eggs, they create mechanical damage.