APHIS. INSECTS. 327 



TRIBE III. APHIDII. 



Antennae with six or seven joints ; elytra and wings sloping, tri- 

 angular, and without fringes ; tarsi with two joints, the first 

 of which is short, and the second terminated by two hooks. 



Some of this tribe undergo a complete metamorphosis. The abdomen in the greater 

 number has at its posterior extremity two eminences in the form of horns or tuber- 

 cles. Many live in gall-nuts. 



I. Metamorphosis incomplete. *. 



Gen. APHIS, MYZOXYLUS, (body covered with white down ; antenna very short) 



II. Metamorphosis complete. 

 Gen. ALEYRODES. 



Gen. APHIS, Lin. Lat. 



Elytra of the same consistence ; rostrum elongated and distinct ; 

 antennas almost setaceous, without setae at the end, of six or 

 seven joints, of which the third and fourth are longest ; tarsi 

 with two joints ; body soft ; abdomen oval, with two tubercles 

 at the extremity. 



The Aphides are small insects, met with in great numbers upon almost all plants. 

 They move but seldom, and they are found in numbers together on the stalks and 

 leaves. Several singular facts have been observed with regard to these insects. The 

 females of the same species are sometimes found apterous, and sometimes with wings ; 

 and both of these descriptions of females at one period of the year deposit their ova, 

 and at another bring forth living young. These females couple in autumn, and 

 after this they are oviparous ; during summer they are viviparous. It appears also, 

 from the observations of Bonnet, Reaumur, and Lyonnet, that the female once im- 

 pregnated can transmit this influence to her female descendants for many generations. 

 Almost all the Aphides are covered more or less with a cottony down. Wherever 

 Aphides are found ants may also be expected. They are attracted by the saccharine 

 liquid which exudes continually from the two tubercles at the end of the abdomen. 

 This liquid, which is limpid and transparent, thickens on exposure to the air ; and 

 Reaumur says it is as sweet as honey, and of an agreeable taste. Many expedients 

 are used in green-houses and hot- houses to destroy the Aphides which infest the plants. 



A. ulmi, Lin. Body cylindrical,, brown, covered with farina ; wings 

 very long, sloping like a roof, with a small brown spot in the mid- 

 dle of the exterior border ; tubercles of the abdomen short. In- 

 habits Europe, on the elm. Nouv. Diet, xxviii. 254. 



FAMILY V. GALLINSECTA. 



Tarsi with one joint, terminated by a single hook. Males with 

 two wings, or two elytra, and want the rostrum. The females 

 are apterous, fix themselves for the most part at the period 

 of depositing their ova, and take the figure of a gall which 

 covers the ova ; antennae composed of eight or nine joints in 

 some, of eleven in others, and sometimes twenty-two to twen- 

 ty-four. 



Gen. DORTHESIA, Coccus, MONOPHLEBA, (antennae moniliform, with about 

 twenty-two joints.) 



Gen. Coccus, Lin. Lat. 



Tarsi with one joint, and terminated by a single hook ; male 

 destitute of a rostrum, with two wings covering the body ho- 

 rizontally ; abdomen terminated by two setae ; female apte- 



