ABSTRACT
C ertainly it was no great evolutionary problem for certain barklice (Psocoptera) of long ago to evolve from scavengers on debris in bird nests to crea-
tures living as ectoparasites on the birds themselves. These chewing lice, which now feed on their bird hosts and on some mammals, are placed in this separate order because of their specialized adaptation for ectoparasitic life. A study of the classification of these insects and that of their bird hosts shows some interesting parallels and has led entomologists and ornithologists to believe that as the bird groups evolved, so did the lice, a one-sided "coevolution."
