CLASSIFICATION 



f erred to the abdominal region. Tarsi one- or two-segmented. Abdomen 

 usually short and broad, eight- to ten-segmented. Cerci absent. 



FIG. 19. Pteronarcys regalis. A, nymph (after NEWPORT); B, imago. Slightly reduced. 



VV 



FIG. 20. Hexagenia variabilis. A, nymph; J5, imago. Natural size. 



Biting lice, or bird lice, parasitic on birds and a few mammals, feeding 

 on feathers, hair or skin. Example, Menopon (Fig. 18). More than 

 fifteen hundred species have been described. 



