130 THE BUTTERFLY VIVARIUM. 



After having watched the long progress and va- 

 rious metamorphoses of an insect, from the egg to 

 its complete or final state, an interesting question 

 arises as to how long the perfected creatures are 

 destined to enjoy the existence for which such 

 elaborate preparations have been made. The 

 answer, from our imperfect knowledge and appre- 

 ciation of the wonderful code of the divinely 

 created laws of Nature, appears at a glance sin- 

 gularly unsatisfactory ; and when we are told that 

 the Ephemera, after passing several years in their 

 preparatory larva state, are destined, in their per- 

 fect form, only to exist afew hours ! we are but too 

 apt to express an ignorant surprise. Such sur- 

 prise, however, will not serve to explain the 

 mystery. 



The common House-fly exhibits an apparent 

 discrepancy almost as great in the opposite direc- 

 tion. After passing most rapidly through the egg, 

 larva, and pupa states to the imago, in three or four 

 days, it lives several weeks in its perfect state ; and 

 those which come forth late in autumn even live 

 through the winter, though in a semi-dormant state, 

 to come from their retreats with the early spring 

 weather, and live a second period of their perfected 

 existence in another season. 



