IV. 



BUTTERFLIES AS BOTANISTS 



Knowledge of the food plants of the cater- 

 pillars of butterflies is of prime importance to one 

 who wishes to study their life histories ; for al- 

 though some species are polyphagous, others are 

 the most particular creatures in the world and 

 will starve to death if they are not supplied with 

 just what they want. That this is not always 

 the easiest thing to learn may be inferred from 

 the frequent mishaps with the most experienced. 

 And it is no wonder they are sometimes at fault 

 or at a loss, for the one hundred butterflies of the 

 eastern United States and Canada, whose food 

 plants are known, choose their food from more 

 than one third of the families of plants mentioned 

 in Gray's Manual of our botany. 



Fifty-two families are represented ; of these, 

 thirty-two nourish only members of a single one of 

 the four families of butterflies, and as a general 

 rule are therefore of minor significance. Excep- 



