ARTHROPODA. 297 



are Crickets (Gryllus), Locusts (Locusta), Grasshoppers 

 (Acrydium), Walking-sticks (Phasma), and Cockroaches 

 (Blatta). 



3. Hemiptera, or " Bugs," are chiefly characterized by 

 a suctorial mouth, which is produced into a long, hard, 

 beak, in which mandibles and maxillae are modified into 

 bristles and enclosed by the labium. The four wings are 

 irregularly and sparsely veined, sometimes wanting. The 

 body is flat above, and the legs slender. The larva differs 

 from the imago in wanting wings. In some species the 

 fore -wings are opaque at the base and transparent at 

 the apex, whence the name of the order. Some feed on 

 the juices of animals, others on plants. Here belong the 

 wingless Bed-bug (Cimex) and Louse (Pediculus), the 

 Squash-bug (Coreus), Water-boatman (Notonecta), Seven- 

 teen-year Locust (Cicada), Cochineal (Coccus), and Plant- 

 louse (Aphis). 



4. Coleoptera, or " Beetles." This is the largest of the 

 orders, the species numbering about ninety thousand. 

 They are easily recognized by the elytra, or thickened, 



Fio. 267. , imago, and b, larva, of the Goldsmith Beetle (Cotalpa lanigera); c, 

 papa of June-bug (Lachnoaterna fusca). 



horny fore-wings, which are not used for flight, but serve 

 to cover the hind pair. When in repose, these elytra are 

 always united by a straight edge along the whole length. 

 The hind wings, when not in use, are folded transversely. 



