APHIS. 169 
are also themselves impregnated, and thus the 
breed may be continued as before mentioned. 
This wonderful faculty in the insects of the pre- 
sent genus appeared, at its first publication, so 
extraordinary as to excite no small degree of 
scepticism in the philosophical world. The ob- 
servations however of Bonnet, Reaumur, Lyonett, 
and others have amply confirmed its truth. Lee- 
wenhoek had long before observed that these in- 
sects were viviparous. Bonnet, whose observa- 
tions were continued with the utmost accuracy, 
assures us that the female Aphides continue to 
produce their young throughout the whole sum- 
mer; that the males appear only in autumn; and 
that the females are at that period oviparous. The 
ova which are thus deposited during the autumn 
do not hatch till the succeeding spring. It is 
however uncertain whether the same individual 
insects which have produced perfect young during 
the summer become oviparous during the autumn, 
or whether the oviparous autumnal oneg ever pro- 
duce living young; the preceding observations 
relating only to the species at large. 
The Aphides in general are very prolific insects. 
Reaumur computes that each Aphis may produce 
about ninety young, and that, in consequence, in 
five generations, the descendants from a single 
insect would amount to five thousand nine hundred 
and four million, nine hundred thousand. 
The Aphides are very prejudicial to many trees 
and plants by absorbing the juices of the tender 
shoots and leaves, which latter they cause to 
