236 H EMITTER A. 



the hinder extremity with two little tubes, knobs, or pores, 

 from which exude almost constantly minute drops of a fluid 

 as sweet as honey ; their heads are small, their beaks are 

 very long and tubular, their eyes are globular, but they have 

 not eyelets, their antennae are long, and usually taper to- 

 wards the extremity, arid their legs are also long and very- 

 slender, and there are only two joints to their feet. Their 

 upper are nearly twice as large as the lower wings, are 

 much longer than the body, are gradually widened towards 

 the extremity, and nearly triangular; they are almost ver- 

 tical when at rest, and cover the body above like a very 

 sharp-ridged roof. 



The winged plant-lice provide for a succession of their 

 race by stocking the plants with eggs in the autumn, as 

 before stated. These are hatched in due time in the spring, 

 and the young lice immediately begin to pump up sap from 

 the tender leaves and shoots, increase rapidly in size, and 

 in a short time come to maturity. In this state, it is found 

 that the brood, without a single exception, consists wholly 

 of females, which are wingless, but are in a condition imme- 

 diately to continue their kind. Their young, however, are 

 not hatched from eggs, but are produced alive, and each 

 female may be the mother of fifteen or twenty young lice 

 in the course of a single day. The plant-lice of this second 

 generation are also wingless females, which grow up and 

 have their young in due time ; and thus brood af:er brood 

 is produced, even to the seventh generation or more, with- 

 out the appearance or intervention, throughout the whole 

 season, of a single male. This extraordinary kind of prop- 

 agation ends in the autumn with the birth of a brood of 

 males and females, which in due time acquire wings and 

 pair ; eggs are then laid by these females, and with the 

 death of these winged individuals, which soon follows, the 

 race becomes extinct for the season. 



Plant-lice seem to love society, and often herd together 

 in dense masses, each one remaining fixed to the plant by 



