I've been volunteering this summer in the Ada County Master Gardener Lab. The public brings in plant and bug questions. Look what came in today. This is a horntail (pigeon tremex) - a type of wood wasp that loves to lay eggs in dying trees. It was discovered in a dead maple, and the man who brought it in thought it might have killed his tree. It didn't. It only attacks trees that already dying or dead. BTW - this wasp doesn't sting. The "tail" is the female's ovipositor.