METAMORPHOSIS OF 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 larve, 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 im 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- 
tishment 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” (Zoo. § 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 
