INSECT A. 573 



V. CoLEOPTERA DiMERA. — The tarsal joints are only 

 three in number. The genera hitherto determined amount 

 only to two, as Claviger and Pselaphus. The latter, how- 

 ever, has been recently constituted into a family, Pselaphi- 

 dae, including Pselaphus, Euplectus, Bythenus, Areopa- 

 gus, Tychus, and Bryaxis. 



Order II. — Dermaptera. 



In this order, the elytra are short and coriaceous, with a 

 straight suture. The wings are membranaceous, with 

 longitudinal ribs, connected in the margin by a transverse 

 one ; they are folded when at rest longitudinally and trans- 

 versely. The mandibles are bidentate. The maxillae have 

 a scaly cylindrical appendix or galea. There are no pylo- 

 ric caeca. The tarsal joints are three in number. The 

 metamorphosis is semicomplete. This class compre- 

 hends the following genera : Forficula, Labia, and Labi- 

 dura. 



Order III. — Orthoptera. 



The elytra, in the insects of this order, are coriaceous, 

 and at their inner margin overlap each other. The under 

 wings are membranaceous, and have numerous longitu- 

 dinal ribs crossed alternately at right angles by many 

 transverse ones, so that their reticulations, or little squares, 

 are usually arranged like bricks in a wall ; when at rest 

 these are folded longitudinally, and unfold like a fan. The 

 parts of the mouth are similar to the coleoptera, with the 

 addition of the galea protecting the maxillae at the sides. 

 The alimentary canal is furnished with a membranaceous 

 crop, and a muscular stomach, armed with corneous scales. 

 The pyloric cceca receive the biliary vessels, a few of which 

 likewise terminate in the intestine. The larvae exhibit u 



