IO 



ENTOMOLOGY 



(small in Phasmidae). Wings two pairs as a rule, though not infre- 

 quently reduced or absent. Fore wings coriaceous (leathery, forming 

 tegmina); hind pair membranous, ample, closely reticulate, plicate 

 along the numerous radiating principal veins. 

 Abdomen with ten evident segments and traces of 

 eleven or twelve. Cerci one- to eight-segmented. 

 Terrestrial and mostly phytophagous. Seven 

 families: Blattidae, Mantidae Gryllidae, Grylloblat- 

 tidae, Tettigoniidae (formerly Locustidae), Locus- 

 tidae (formerly Acridiidae, Fig. 14), Phasmidae (Fig. 

 243). More than ten thousand species are known. 

 4. Dermaptera. Metamorphosis direct. Eyes 

 facetted, reduced, or absent. Antennae long, filiform, 

 with ten to fifty segments in adults. Mouth parts 

 mandibulate, prognathous; lingua and superlinguae 

 well developed; labium split to the mentum; para- 

 glossa united with glossa of same side. Prothorax 

 large. Thoracic segments distinct. Tarsi three- 

 segmented. Elytra short, scale-like, meeting in a 

 straight line. Wings projecting from under the 

 elytra, ear-shaped, with many radiating principal 

 veins, folding plicately, also twice transversely. 

 Abdomen with eleven segments, the tergites and 

 sternites strongly, and complexly imbricate laterally, with a terminal 

 pair of forceps (cerci). Wingless species numerous. Some four hun- 

 dred species are at present known. 



Three suborders, each represented by one family : Arixeniidae (one 

 species) ; Hemimeridae, containing 

 a single African species (Fig. 15), 

 which is flattened, eyeless, wing- 

 less, with long unsegmented cerci, 

 viviparous, and parasitic on the rat; 

 and Forficulidae, formerly a family 

 of Orthoptera. 



5. Platyptera. Metamorphosis 

 direct. Mouth parts mandibulate. 

 Wings, if present, two pairs, delicate, 



membranous, equal or hind pair smaller, and with the principal veins 

 few and simple. Abdomen with usually ten evident segments and 

 often traces of an eleventh. Integument usually thin. Nymphs thy- 

 sanuriform. Five suborders. 



FIG. 12. The snow 

 flea, Achorutes nivicola. 

 Length, 2 mm. 



FIG. 



13. Sminlhurus horiensis. 

 1.2 mm. 



Length, 



