The Pediculoididae are so strongly sexually dimorphic that there is little resemblance between the sexes, necessitating two sets of keys. As I am particularly interested in the females, they only are here discussed.

In Pediculoides the abdomen tapers posteriad to a blunt point, in all the other genotypes the abdomen is more or less truncate and angular behind. Pygmephorus (often misspelled) has tarsi I swollen and much longer than tibiae I. In Pediculopsis they are subequal. Resinacarus also has large tarsi I. In figure 12 the line around the middle of tarsi I is to be taken as a constriction rather than a segmental boundary. The bristles of legs I are not identical in figures 9 and 12, nor are the bristles of dorsal plates I and III. Resinacarus has three pairs of prothoracic bristles while the type of Pygmephorus has two pairs.