12 



ENTOMOLOGY 



spinneret. Thorax elongate; prothorax small. Tarsi three-segmented. 

 Wings (sometimes absent) two pairs, elongate, similar, equal, mem- 

 branous, delicate, with few and feebly developed longitudinal and cross 

 veins ; not folded. Abdomen elongate, with ten segments and frequent- 

 ly an eleventh tergite, and a pair of short stout biarticulate cerci. 



Integument delicate. Feeble insects, 

 not social in habit. Examples, 

 Embia, Oligotoma (Fig. 16). Some 

 twenty species, all from warm 

 climates. 



Suborder Zoraptera. Eyes ves- 

 FIG. 17. Psocus venosus. Length, 5 mm. tigial or absent. Antennae monili- 



f orm, nine-segmented. Thorax long, 



as long as the abdomen; prothorax large, larger than the meso- and 

 metathorax combined. Tarsi two-segmented. Apterous, or with two 

 pairs of wings; the fore wings with a few irregular veins and cells. 

 Abdomen with ten evident segments; the tenth and eleventh united 

 dorsally. Cerci short, one -segmented. Minute, active forms (little 

 more than two millimeters in length), terrestrial, 

 predaceous. One genus, Zorotypus, represented 

 by three Oriental species (Africa, Ceylon, Java), 

 one species from Costa Rica and two from the 

 United States. 



These insects are most nearly related to Isop- 

 tera and Corrodentia. 



Suborder Corrodentia. Eyes facetted. An- 

 tennae filiform, with thirteen to fifty or more 

 segments. Mouth parts hypognathous. Pro- 

 thorax reduced. Tarsi two- or three-segmented. 

 Wings present, rudimentary or absent; fore pair the 

 larger; veins few and irregular. Abdomen short 

 and stout, with nine or ten segments. Cerciabsent. FIG. IB. A chicken 

 Integument delicate. Small terrestrial insects, louse> Men P n - Length, 



' 2 mm. 



including the book lice and other psocids. 



Example, Psocus (Fig. 17). More than two hundred species are 



known. 



Suborder Mallophaga. Small wingless flattened insects of parasitic 

 habit. Head large. . Eyes of a few isolated ocelli, or vestigial, or 

 absent. Antennae three- to five-segmented. Mouth parts prognathous. 

 Prothorax distinct; meso thorax often, and metathorax usually, trans- 



