MOTIONS OF INSECTS. 351 
and generally speaking, but not invariably, in Gryllus, F. 
and Truaxalis,—the left elytrum laps over the right: but 
in Mantis, F.; Mantispa, Latr.; some female Locust ; 
Acheta; and Gryllotalpa, Latr.; 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 intersected 
alternately by transverse ones, which thus form quadran- 
gular 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 (Acheta domestica, I.) fly with 
an undulating motion, like a woodpecker, alternately 
ascending with expanded wings, and descending with 
folded ones*. The field- and mole-crickets (Acheta cam- 
pestris and Gryllotalpa, F.), as we learn from Mr. 
White>,—and, since the structure of their wings is simi- 
lar, 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 or 
The former division includes the Cicadiade; Aphis; 
Chermes; Thrips; and Coccus;—and the latter the 
a Hist. Ins. 63. b Nat. Hist. ii. 82. 
¢Prate IL, Fic. 4. 4 Prare X. Fie. 3. Uf. Fie. 5. 
