132 THE BUTTERFLY VIVARIUM. 



and abdomen to assume by slow progressive growth 

 their eventual forms. In this state the insect is 

 generally quite white, even when destined to become 

 the blackest of Beetles — and appears of the consist- 

 ence and colour of a skinned almond. It is not till 

 the full size of the wing-cases has been attained, and 

 till after their partial hardening to the proper horny 

 texture, that the insect is enabled to make its escape 

 from its cocoon, when it still remains, for some time 

 after its exposure to the air, nearly white; the proper 

 colour being, however, soon assumed. In the insects 

 which have no decided metamorphosis, the three 

 stages of larva, of active pupa or nymph state, and 

 the acquiring of the final form, are so blended one 

 into the other, that it is difficult to assign a special 

 period at which the one terminates and the other 

 begins. 



Having now traced the course of several classes 

 of insects from the egg, to the perfect or imago 

 state, I shall proceed at once to speak of Butterflies 

 in that phase of their beautiful existence. The term 

 imago was adopted by Linnaius in extreme contra- 

 distinction to that of larva. The last-named term 

 expressing the idea that the caterpillar was a 

 masked* stage of existence, while in the winged 



* See ante, page 64. 



