Springtails (Order Collembola) form the largest of the three orders of modern hexapods (along with the Protura and Diplura) that are no longer considered insects. The three orders are sometimes grouped together in a class called Entognatha because they've internal mouthparts, but they don't appear to be more closely related to one another than to insects, which have external mouthparts. Recent genetic studies suggest that Collembola are a separate evolutionary line from the other Hexapoda . Mem… (More on Collembola)