Order: Plecoptera.
Biting mandibles; second maxillae incompletely fused. Fore-wings similar in texture to hind-wings, whose anal area folds fanwise. Jointed, often elongate, cerci. Numerous (50-60) Malpighian tubes. Young resembling parents, but aquatic in habit, breathing dissolved air by thoracic tracheal gills.
Includes the single family of the Perlidae (Stone-flies), formerly grouped with the Neuroptera.
Order: Isoptera.
Biting mandibles; second maxillae incompletely fused. Fore-wings similar in shape and texture to hind-wings, which do not fold. In most species the majority of individuals are wingless. Short, jointed cerci. Six or eight Malpighian tubes. Young resembling adults; terrestrial throughout life.
Includes two families, formerly reckoned among the Neuroptera—the Embiidae and the Termitidae or “White Ants” (see [Termite]).
Order: Corrodentia.
Biting mandibles; second maxillae incompletely fused; maxillulae often distinct. Cerci absent. Four Malpighian tubes.
Includes two sub-orders, formerly regarded as Neuroptera:—
1. Copeognatha: Corrodentia with delicate cuticle. Wings usually developed; the fore-wings much larger than the hind-wings. One family, the Psocidae (Book-lice). These minute insects are found amongst old books and furniture.