any of a group of about 800 species of small primitive wingless insects, considered by some entomologists to have features similar to ancestral insects. In some classification schemes, the order Diplura is considered to be in the subclass Apterygota of the class Insecta, while in others it is placed in its own subclass (Entognatha) of the superclass Hexapoda. Diplurans are blind, pale insects that live in soil and feed on decaying vegetation and plant tissues, occasionally damaging growing plants.