HEMIPTERA. 5/1 



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

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

 meniliranous vesiele, accompanied beneath by two nngnes. Four broad pieces, which are the sheaths of 

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

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

 a gummy sacchatine nature. 



Some species, by puncturing ve.i^etables to extract the sap, produce in various parts, especially in the flowers and 

 buils, monstrosities, bavin^r the appearance of ;;alls. In this number is Psylla Buxi, figured by Ri^^aumur, 

 JShuii. fns.y vol. iii. pL 19, li;,^ 1—14, winch is found on the box. The alder, fi^, nettle, &c. produce other 

 species. 



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

 of Livla. The antennre are much thickened at the base. 



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

 esting- British species.] 



The other Apliiilii have only six or eight joint.s in the aniennrc, the last of which is not lenuinated 

 by two set;c. 



Snmetimcs the wing-covers and wings are linear, fringed with hairs, and carried horizontally iipoa 

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

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

 joints. Such is the genus 



TriRiPS, Linn.,— 

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

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

 They live upon Ihjwers 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 month exhibited to him characters 

 £>J\f which appeared essentially to distinguish the species of Thrips from the other insects of 

 "■ !—^ this order. M. Strauss also, who had studied them with admirable precision, considered 

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

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

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

 of the month in my Mod&im Clossif cation of Insects, vol. ii. p. 1, with figures. Mr. 

 i'.ut\--Ti]rip.s. jiaiidi^y i;iag 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 

 d-'flexed at the sides like a roof; the rostrum is very distinct ; the tarsi are terminated by two ungues; 

 and the antenna; 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. 



'I'iiey live mostly in society upon tre&s and plants, which they suck with their proboscis. They do not leap, and 

 ciaul 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 uf plant-lice always apterous, and of pups [ilemi-nym plies], of which the 

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

 >'Oung, which are ejected tail foi'emost, without any previous coupling. The males, 

 amongst which some are winged and some wingless, 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 \\hich 

 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, capable of 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 

 nini' 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 young buds of ths 

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

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



A\ 



