10 



ENTOMOLOGY 



FIG. 16. Psocus venosus. Length, 5 mm. 



Embia, Oligoloma (Fig. 15). Some twenty species, all from warm 

 climates. 



These insects are most nearly related to Termitidae and Psocidae. 

 Psocidce. Eyes facetted. Antennae 13-50 jointed. Mouth parts 

 hypognathous. Prothorax reduced. Wings present, rudimentary or 



absent; front pair the larger; 

 veins few and irregular. Abdomen 

 with nine or ten segments and no 

 cerci. Integument delicate. Ex- 

 ample, Psocus (Fig. 1 6). About 

 two hundred species. 



Comstock raises Psocidae to the 

 rank of an order, for which he em- 

 ploys, in a new sense, Brauer's term Corrodentia. 



Suborder Mallophaga. Wingless flattened insects, of parasitic 

 habit. Head large. Eyes consisting of a few isolated ocelli or else ab- 

 sent. Antennae 3-5 jointed. Mouth parts prognathous. Prothorax dis- 

 tinct; mesothorax often and metathorax usually transferred to the ab- 

 dominal region. Abdominal segments eight to 

 ten in number; no cerci. Parasitic upon birds 

 and a few mammals. Example, Menopon (Fig. 

 17). More than fifteen hundred species have 

 been described. 



Packard's order Platyptera originally included 

 Perlidae. Brauer's order Corrodentia consisted 

 of Termitidae, Psocidae and Mallophaga; Perlidae 

 being set apart as an order (Plecoptera} and Em- 

 biidae being transferred doubtfully to Orthop- 

 tera. 



Enderlein's thorough studies confirm the 

 view that Termitidae, Embiidae, Psocidae and 

 Mallophaga constitute a single order. 



5. Plecoptera. - - Metamorphosis direct. 

 Antennae long, multiarticulate. Mouth parts 

 mandibulate. Prothorax large. Wings two 



pairs, membranous, coarsely and complexly reticulate; equal or else hind 

 wings larger and with an ample plicate anal area. Abdomen with ten 

 segments and usually a pair of long multiarticulate cerci. Nymphs thy- 

 sanuriform, aquatic; adults unique in having tracheal gills. Example, 

 Pteronarcys (Fig. 18). A single family, Perlidae, comprising two hundred 

 species. 



FIG. 17. A chicken 

 louse, Menopon. Length, 

 2 mm. 



