*HE ROSE APHIS* 307 



strengthened, it is set down on some tender shoot, 

 and there left to provide for itself. 



In the spring months there appear but these two 

 generations of the Aphis : the warmth of summer* 

 however, produces no less than five. One of these 

 comes forth in May, and the months of June and 

 July supply each two more. The insects of the 

 May breed cast their skins twice, and the others 

 three or four times, according to the warmth of 

 the season. When the heat has been sufficiently 

 great, and the food in tolerable plenty, the first 

 change has been observed to take place in about 

 ten days alter their production. 



Early in June some of the third generation, which 

 were produced about the middle of May, after cast- 

 ing their last covering, discover four erect wings 

 much longer than their bodies. The formation of 

 the wings seems to depend not on sexual distinction, 

 nor even on the original structure of the insects, so 

 much as on the quantity and quality of the nourish- 

 ment with which they are supplied. Few of those 

 on succulent shoots have wings, while those of the 

 same generation on the less tender branches are 

 most of them winged. Some time before they 

 come to their full growth, it is easy to discern which 

 of them will have wings, from a remarkable fullness 

 of the breast. When the last covering is rejected, 

 the wings, which were before folded in a very nar- 

 row compass, gradually extend in a most beautiful 

 manner to their proper size and dimensions. All 

 the following breeds are winged. 



In the autumn the eighth, ninth, and tenth gene- 

 X 1 



