504 INVERTEBRATE MORPHOLOGY. 



II. SUBCLASS PTERYGOTA. 



The members of the subclass Pterygota are, as the name 

 indicates, typically provided with wings, though in a compar- 

 atively few cases these structures may have disappeared 

 through degeneration due to parasitic habits, or through special 

 adaptation to certain conditions of life, as in the neuters of 

 the Ants and Termites. In nearly all cases the larvae differ 

 in form from the adults, and various grades of metamorphosis 

 are found. 



1. Order Dermaptera. 



The Dermaptera or Earwigs (Fig. 233) are usually small 

 insects which resemble not a little the Thysanura. The 

 abdomen terminates in a pair of forceplike 

 processes termed cerci, their shape suggesting 

 the generic name Forficula, applied to certain 

 members of the order. The anterior wings are 

 small and chitiuous and serve as covers for 

 the protection of the posterior pair, which are 

 larger, membranous and veined, and when at 

 rest are folded longitudinally like a fan, and in 

 FIG. 233. Zato addition twice transversely, so that they are 

 almost completely hidden by the scalelike an- 

 terior pair. The antennae are long and filiform, 

 and the mouth-parts adapted for biting. The Earwigs are 

 terrestrial forms and pass through a gradual metamorphosis. 

 In many respects they approach nearer the Thysauura than 

 any other insects, and are related rather closely to the suc- 

 ceeding order. 



2. Order Orthoptera. 



In this order, which includes the Locusts, Grasshoppers, 

 (Caloptenus), Crickets (Gryllus), Cockroaches (Periplaneta), 

 and other forms, the mouth-parts are adapted for biting and 

 the last segment of the abdomen bears two-jointed cerci. The 

 anterior wings form, as in the Dermaptera, covers for the 

 posterior pair and are chitinous plates; the posterior ones are, 



