Minute Aptera, in which the mouth is formed for biting, and is furnished with mandibles and maxillae.

The members of this order (fig. 180, B) are commonly known as "Bird-lice," being parasitic, sometimes upon Mammals, but mostly upon Birds. They strongly resemble the Pediculi, but the mouth is formed for biting, to suit their mode of life - since they do not live upon the juices of their hosts, but upon the more delicate tegumentary appendages. They are sometimes regarded as constituting a degraded group of the Hemiptera.