156 



METAMORPHOSIS 



while the B states are not to be recognised as equivalent condi- 

 tions. 



Every Insect after leaving the egg undergoes during the 

 process of growth castings of the skin, each of which is called 



FIG. 84. Locust 

 (Acridium per- 

 eyrinum] : A, 

 newly hatched ; 

 B, just ante- 

 cedent to last 

 ecdysis ; C, per- 

 fect Insect. 



a moult or ecdysis. Taking for our present purpose five as the 

 number of ecdyses undergone by both the locust and butterfly, 

 we may express the differences in the successions of change we 

 portray in Figs. 84 and 85 by saying that previous to the 



FIG. 85. Butterfly (Pieris) : 



A, the newly hatched 

 young, or larva magnified ; 



B, pupa (natural size) just 

 antecedent to last ecdysis ; 



C, perfect Insect. 



first ecdysis the two Insects are moderately dissimilar, that the 

 locust undergoes a moderate change before reaching the fifth 

 ecdysis, and undergoes another moderate change at this moult, thus 

 reaching its perfect condition by a slight, rather gradual series of 



