282 



MOTIONS OF INSECTS. 



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 intersected 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. Bay tells us that both sexes of 

 the house-cricket (Gryllus domesticus) fly with an undulating 

 motion, like a woodpecker, alternately ascending with ex- 

 panded wings, and descending with folded ones. 1 The field 

 and mole-crickets ( Gryllus campestris and Gryllotalpa vul- 

 garis), as we learn from Mr. White 2 , — 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 ' — and those in which the base and the apex are 

 of different substances; the first being generally corneous, 

 and the latter membranaceous. 4 The former or homopterous 

 division includes the Cicadarice Latr., Aphis, Chermes, 

 Thrips, and Coccus ; — and the latter the heteropterous di- 

 vision, comprehending, besides the Gcocorisa Latr., Notonecta, 

 Sigara, Nepa, Ranatra, and Naucoris of Fabricius. The 

 posterior tibia? of some of this last division (Lygceus phyllopus, 

 foliaceus, &c. F.) are furnished on each side with a foliaceous 

 process — which may act the part of outriggers, and assist 

 them in their flight. 5 I can give you no particular informa- 

 tion with respect to the aerial movements of the insects of 

 this order : the British species that belong to it are generally 

 so minute that it is not easy to trace them with the naked 

 eye ; and unless some kind optician, which is much to be 

 wished, would invent a telescope by which the proceedings 

 of insects could be examined at a distance, there is no other 

 way of studying them. 



1 Hist. Ins. 63. 

 3 Plate II. Fig. 4. 



5 I have separated this tribe from the 

 K. Ms. 



2 Nat. Hist. ii. 82. 

 4 Plate II. Fig. 5. 

 rest under the name of Petalopu 



