METAMORPHOSIS OP INSECTS. 571 



had been stored-up within the body of the larva. "When the 

 development of the wings, legs, &c. has been completed, the 

 Imago or perfect insect bursts-forth from' its pupa-case, and 

 enters upon the life of activity for which it is destined. In 

 this condition alone does it possess proper generative organs ; 

 and the business of rearing the larvae, or of preparing a habi- 

 tation in which they shall find a store of food laid-up for 

 them, seems generally one of the principal objects of its 

 existence. In many instances, indeed, as in the Silkworm, 

 the Imago takes no nourishment whatever, and dies as soon 

 as the generative act has been completed, and the fertilized 

 eggs have been deposited. It is scarcely possible to find a 

 greater contrast than that which exists between the footless 

 Maggot, almost destitute of the power of movement, and 

 having no capacity but that of gorging itself with the nou- 

 rishment provided for its sustenance, and the active Bee, 

 almost constantly on the wing, darting from flower to flower 

 in search of the honied sweets which it is now content to 

 sip, and coming home to toil in the construction of that 

 wonderful edifice which human skill could have scarcely 

 rivalled, certainly not surpassed. And it is evident that the 

 true way of looking at the metamorphoses of Insects, is, to 

 consider the chrysalis condition as a continuation of the de- 

 velopmental process which takes place within the egg ; the 

 larva being adapted to come forth into the world for a time 

 in a very immature condition, that it may obtain for itself 

 such a supply of nutrient material as could not have been 

 stored up within the egg, without adding so greatly to its 

 bulk, as to render impossible that enormous multiplication in 

 the number of eggs which is so characteristic a phenomenon 

 in the history of this class. 



746. A remarkable departure from the method of sexual 

 propagation common among Insects, has long been known to 

 occur in the tribe of Aphides, or "plant-lice" (ZooL. 785); 

 which multiply themselves while yet in a state of develop- 

 ment that may be considered as larval, without any proper 

 generative act. No distinction exists between males and 

 females, but every individual is formed upon the ordinary 

 female type ; and eggs are produced from an ovarium, which 

 are hatched within the body, so that the young come forth 

 alive. These in their turn repeat the same process within a 



