HEMIPTERA, 181 
Here the antenne are composed of from ten to eleven joints, the 
last of which is terminated by two sete. 
They possess the faculty of leaping, and form the genus 
Psytia, Geof?.—Cuermes, Lin. 
These Hemiptera, also called pseudo-aphides, or faux-pucerons, live 
on the trees and plants from which they derive their nourishment ; 
both sexes are furnished with wings. Their larve usually have a 
very flat body, broad head, and the abdomen rounded posteriorly. 
Their legs are terminated by a little membranous vesicle accom- 
panied beneath with two hooks. Four wide and flat pieces, which 
are the sheaths of the elytra and wings, distinguish the nymph. 
Several in this state, as well as in the first, are covered with a white 
substance resembling cotton, arranged in flakes. ‘Their feeces form 
threads cr masses, of a gummy and saccharine nature. 
Some species, by wounding plants in order to suck their juices, 
produce excrescences somewhat resembling gall-nuts, particularly on 
their leaves or buds. Of this number is the 
P.buxi; Chermes buxi, L.: Reaum., Mem., Insect., II, xix, 
1,14. Green, with brown- yellowish wings. 
Other species are also found on the Alder, Fig tree, Nettle, &c.* 
A species which lives in the flowers of the rushes has been 
erected into a genus by Latreille, under the name of Livia. The an- 
tennze are much thicker inferiorly than at their extremity f. 
The remaining Aphidii have but six or eight joints in the an- 
tenn; the last is not terminated by two setz. 
Sometimes the elytra and wings are linear, fringed with hairs, and 
extended horizontally on the body, which is almost cylindrical; the 
rostrum is very small or but little distinct. The tarsi are terminated 
by a vesicular joint without hooks. The antennz consist of eight 
graniform joints. Such are the Insects which form the genus 
Tueies, Lin. 
They are extremely agile, and seem to leap rather than fly. When 
we irritate them beyond a certain point they turn up the posterior ex- 
tremity of their body in the manner of the Staphylini. They live on 
flowers, plants, and under the bark of trees. The largest species 
scarcely exceed one line in length ¢ 
Sometimes the elytra and wings, oval or triangular, and without a 
fringe of hairs along the margin, are inclined or tectiform. The ros- 
* See Fab., Geoff., De Geer. 
+ Lat., Gen. Crust. et Insect., III, p.i70; Arh., Faun. Insect., VI, 21 
+ See Lat., Ibid. p. ead. and the authors already quoted. In the organization of 
the mouth, I have detected characters which seem to distinguish it essentially from 
that of Insects of this order. M. Straus, who has studied it with admirable minute- 
ness, thinks that Thirps belong to the order of the Orthoptera. 
