182 INSECTA. 



trum is very distinct. The tarsi are terminated by two hooks, and 

 the antennae have but six or seven joints. Such is the genus 



Aphis, Lin. 

 Which we divide in the following manner : 



Aphis, 



Properly so called, where the antennae are longer than the thorax 

 and consist of seven joints, the third of which is elongated ; the eyes 

 are entire, and there are two horns or mamillae at the posterior extre- 

 mity of the abdomen. 



Almost all of them live in society on trees iand plants, of which 

 they suck the juices with their trunk. The two horns observed at 

 the posterior extremity of the abdomen in a great number of species 

 are hollow tubes from which little globules of a transparent, honey- 

 like fluid frequently exude, on which the Ant eagerly feeds. 



In each community, during the spring and summer, Ave find 

 Aphides that are always apterous, and semi-nymphs whose Avings are 

 yet to be developed ; all these individuals are females, Avhich produce 

 living young ones that issue backwards from the venter of their 

 mother, Avithout previous copulation. The males, some of which are 

 Avinged, and others apterous, only apyjear toAA'ards the end of summer 

 or in autumn. They fecundify the last generation produced by the 

 preceding individuals, Avhich consists of unimpregnated apterous fe- 

 males. After coititm the latter lay their eggs on branches of trees, 

 where they remain during the Avinter, and from Avhich, in the spring, 

 proceed little Aphides, Avhich soon multiply Avithout the assistance of 

 the males. 



The influence of a first fecundation is also extended to scA^en suc- 

 cessive generations. Bonnet, to whom Ave are indebted for most of 

 these facts, by isolating the females, obtained nine generations in the 

 space of three months. 



The wounds inflicted on the leaves or tender twigs of plants, by 

 Aphides, cause those parts of the A'egetable to assume a A'ariety of 

 forms, as may be obser\'ed on the shoots of the Lime tree, the leaves 

 of Gooseberry bushes, Apple trees, and particularly those of the Elm, 

 Poplar, Pistachio, in Avhich they produce vesicles or excrescences en- 

 closing colonies of Aphides, and frequently an abundant saccharine 

 fluid. Most of these Insects are covered Avith a farinaceous sub- 

 stance, or cotton-like filaments, sometimes arranged in bundles. The 

 larvije of the Heinerobii, those of several Diptera, and of Coccinellae, 

 destroy immt nse numbers of Aphides. M. A. Duvau has commu- 

 nicated to the Academic des Sciences, the interesting result of his re- 

 searches on these Insects. His Memoir has been inserted in the An- 

 nales du Museum d'Histoire Naturelle. 



A. quercus,h.; Reaum., Insect., Ill, xxviii, 5, 10. BroAvn; 

 remarkable for its rostrum, Avhich is at least thrice as long as 

 the body. 



