Order 7. HEMIPTERA. 571 



from which they obtain their nourishment ; the two sexes are winged ; the larvae have the body gene- 

 rally very flat ; the head broad, and the abdomen rounded behind. Their legs are terminated by a 

 meniliranous vesicle, accompanied beneath by two ungues. Four broad pieces, which are the sheatlis of 

 the wing-covers and wings, distinguish the pupa; : many in this state, as in that of the larva, are 

 covered by a white cottony secretion, arranged iu flakes. Their excrements form threads or masses, of 

 a gummy saccharine nature. 



Some species, by puncturing vegetables to extract the sap, produce in various parts, especially in the flowers and 

 buds, monstrosities, having the appearance of galls. In this number is Pnylla Buxi, figured by Reaumur, 

 Mem. Ins., vol. iii. pi. 19, tig. 1—14, which is found on the box. The alder, tig, nettle, &c. produce other 

 species. 



Latreille has formed with the species which lives in the flowers of Juncus articulatiis, a genus, under the name 

 of Livia. The antennae are much thickened nt the base. 



[.Mr. Curtis has published the tigure of another genus under the name of Livilla, founded upon a small, inter- 

 esting British species.] 



The other Aphidii have only six or eight joints in the antennae, the last of which is not terminated 

 by two setae. 



Sometimes the wing-covers and wings are linear, fringed with hairs, and carried horizontally upon 

 the body, which has nearly a cylindrical form ; the proboscis being small, or scarcely distinct. The tarsi 

 are terminated by a vesicular joint without ungues ; and the antennae have eight somewhat monililorm 

 joints. Such is the genus 



Thrips, Linn.,— 



The species of which are extremely active, and appear to leap rather than fly. When much irritated, 



they elevate and bend the extremity of their bodies into an arch in the same manner as the Staphylini. 



They live upon flowers and plants, and under the bark of trees. The largest species scarcely exceed a 



line in length. 



Latreille observes in a note that the structure of the mouth exhibited to him characters 

 which appeared essentially to distinguish the species of Tlirips from the other insects of 

 this order. M. Strauss also, who had studied them with adtnirahle precision, considered 

 that they belonged to the order Orthoptera. [Subsequently, the genus has been raised 

 to the rank of a distinct order by Mr. Haliday in a valuable memoir published in the En- 

 tomological Magazine, under the name of Thysanoptera, and I have illustrated the structure 

 of the mouth in my Modem Clnssif cation of Insecis, vol. ii. p. 1, with figures. Mr. 



F.i02.--Thrips. f{aliday has established a number of generic and subgeneric divisions.] 



Sometimes the wing-covers and wings are oval or triangular, without a fringe of hairs, and are 



deflexed at the sides like a roof ; the rostrum is very distinct ; the tarsi are terminated by two ungues ; 



and the antennae have only six or seven joints : these form the genus 



Aphis, Linn. 



Aphis, proper, has the antennae longer than the thorax, 7-jointed, the third being elongated; the eyes are entire, 

 and the posterior extremity of the abdomen is furnished with two horns or tubercles. 



They live mostly in society upon trees and plants, which they suck with their proboscis. They do not leap, and 

 crawl but slowly. The two horns at the extremity of the body in many species are 

 tubes, from which frequently exude small drops of a transparent saccharine fluid, 

 [termed honey-dew], of which the ants are very fond. Each society consists in spring 

 and summer of plant-lice always apterous, and of pupae [liemi-nymphes], of which the 

 wings ought to be developed; all these individuals are females, which produce living 

 young, which are ejected tail foremost, without any previous coupling. The males, '^'f- los.— Aphis Rosw. 



amongst which some are winged and some w ingless, appear only at the end of the summer or in autumn. They 

 fecundate the last generation produced from the preceding individuals, consisting of wingless females which 

 require impregnation, after which they deposit eggs upon the branches of trees, which remain in that state all 

 through the winter, from which young plant-lice are produced in the spring, capableof multiplying without union 

 with the males. 



The influence of a single impregnation thus extends through several successive generations. Bonnet, to whom. 

 we are indebted for the majority of the facts observed upon this subject, obtained, by the isolation of females, 

 nine generations in the space of three months. The punctures which the plant-lice make in the leaves and young 

 twigs of vegetables, often cause these parts to assume different forms, as may be seen in the youns buds of the 

 lime, the leaves of the gooseberry, pear, and especially of the elm, poplar, &c., where they produce a kind of vesi- 

 cles or excrescences, containing whole families of plant-lice, and often a saccharine fluid, in the interior. The 



