150 THE INSECT WORLD. 



presents, we must consider the problem which the caterpillar has 

 to solve. In this problem there are two unknown quantities to 

 be discovered. For the first, the caterpillar must suspend itself 

 firmly ; for the second, the pupa, having no communication with 

 the object which supports it, must be suspended in the same 

 manner. This problem is difficult, apparently impossible to solve. 

 It is only by watching these insects at work that one can discover 

 the admirable mysteries of their lives. Swammerdam, Valisnieri, 

 and other observers who have studied insects, had not, however, 

 observed the manoeuvres of caterpillars in this curious phase of 



Figs. 102, 103. Caterpillars of the small Tortoise-shell Butterfly (Vanessa urticee) 

 undergoing their metamorphosis. 



their existence. It is to Reaumur, again, that science is indebted 

 for the most charming and valuable observations on this point. 

 He got together a great number of caterpillars of the small 

 Tortoise-shell Butterfly (Vanessa urticce), black, prickly cater- 

 pillars which are common on the stinging- net tie, where they live 

 in companies, and suspend themselves by the tail. When the 

 time approaches at which the caterpillars of this species ought to 

 undergo their transformations, they usually leave the plant which 

 had up to that time served them as food. After having wandered 

 about a little, they find themselves in some convenient spot, where 

 they hang themselves up head downwards (Figs. 102, 103). 



In order to hang itself in this way, the caterpillar begins by 

 covering, with threads drawn in different directions, a pretty 

 large extent of the surface of the body against which it wishes 



