METAZOA INSECTA. 417 



the genus is especially helpful to teachers and students. 

 The wings in this locust, however, are useless vestiges. 



One of the interesting specializations occurring among 

 the Acridiidae is in the case of the grouse locust, Tettix, 

 (No. 1026). Here the prothorax has grown backward, 

 usurping the place and function of the wing covers, 

 which, no longer needed, have dwindled to tiny rem- 

 nants. 



The Locustidae are represented by the true grasshop- 

 per, Orchelimum vulgare Harris (No. 1027). It lives in 

 grassy meadows and fields, and is a vivid green in color, 

 while the katydid, Cyrtophyllus concavus Say (No. 1028), 

 also green in color, frequents trees and shrubs. In these 

 insects the unconsolidated condition of the thorax is 

 correlated with the weak legs and wings. The latter 

 organs are leaf-like and have no stiff anterior veins. 

 In the katydid the forward wings are so large and con- 

 cave that they encircle the posterior part of the body like 

 a cylinder. The insect opens these wings suddenly and 

 brings them together in such a way as to produce the 

 familiar note "Katydid, she did, Katy didn't." The 

 cone-headed katydid, Conocephalus ensiger Harris (No. 

 1029), has the head extending forward in the shape of a 

 cone. 



The female of Orchelimum (No. 1027) can be readily 

 distinguished from the male by the sword-shaped ovipos- 

 itor. 



Among the specialized Orthoptera are the Gryllidae or 

 crickets. The body in both the larva (No. 1030) and the 

 adult Gryllus (No. 1031) is shortened and black in color. 

 The first pair of wings (No. 1031) are small, horny wing 

 covers, while the second pair are useless in flight The 

 cricket is provided with an ovipositor and a pair of long 

 cerci. 



A remarkable example of adaptation of structure to 

 habit is offered by the mole cricket, Gryllotalpa vulgaris 

 Linn. (No. 1032, dorsal and ventral side). It is ex- 



