MOTIONS OF INSECTS. 347 



right: but in Mantis ; Mantispa ; some female Acridce ; 

 Gryllm ; and Gryllotalpa ; the right is laid over the 

 left. The wings in this order, though always ample 

 and larger than the tegmina, do not invariably form a 

 quadrant of a circle, falling often short of it. They are 

 extended by means of nervures, which, like so many 

 rays, diverge from the base of the wing, and are inter- 

 sected alternately by transverse ones, which thus form 

 quadrangular areas, arranged like bricks in a wall. 

 When at rest, they are longitudinally folded. The 

 flight of these insects, as far as it has been observed, 

 much resembles, it is said, that of certain birds. Ray 

 tells us that both sexes of the house-cricket (Gtyllus do- 

 mesticus] fly with an undulating motion, like a wood- 

 pecker, alternately ascending with expanded wings, and 

 descending with folded ones a . The field- and mole- 

 crickets (Gryllus campestris and Gryllotalpa vulgaris\ 

 as we learn from Mr. White 5 , and, since the structure 

 of their wings is similar, probably the other Orthoptera, 

 fly in the same way. 



Hemipterous insects, with respect to their Hemelytra, 

 may be divided into two classes. Those in which they are 

 all of the same substance varying from membrane to a 

 leathery or horny crust c and those in which the base 

 and the apex are of different substances ; the first being 

 generally corneous, and .the latter membranaceous d . 

 The former or homopterous division includes the Ci- 

 cadari&,~LsitY.; Aphis,- Chermes ; Thrips; audCocctiS; 

 and the latter the heteropterous division, comprehend- 

 ing besides the Geocoris^ Latr., Notonccta / Sigara : 



a Hist. Ins. 63. b Nat. Hist. ii. 82. 



c PLATE II. FIG. 4. * PLATE X. FIG. 3. II. FIG. .5. 



