144 BUTTERFLIES 



and select for her egg-laying a single species of this vexing 

 tribe he replied: "If your butterfly selects only that, it is a 

 better botanist than most of us." 



While later observers have found that this beautiful little 

 insect is not so exclusive in its choice of a food plant as was 

 formerly believed, it serves to illustrate the fact that a 

 large proportion of the caterpillars of this group have a 

 very narrow range of food plants. In nearly every case 

 where the food is thus restricted the insect feeds only upon 

 species which are closely related to one another, generally 

 falling within a single genus according to the classification 

 of the botanists. 



There has been much discussion in regard to the way in 

 which the mother butterfly knows the particular species 

 which she chooses for oviposition. Experiments ap- 

 parently have shown that she is not dependent upon the 

 sense of sight but rather upon the sense of smell, which as 

 is well known is much more highly developed in insects 

 than in the higher animals. I suppose it is not very 

 strange that a creature which has fed from infancy upon 

 leaves with a certain taste and odor should in its later life 

 respond only to that particular odor and should neglect all 

 others. In a way the butterfly itself is a product of the 

 plant and it probably is not necessary to assume that each 

 butterfly differentiates the odors of all kinds of plants but 

 only that she responds to the fragrance of the one with 

 which she has been particularly associated. 



This idea may suggest to various observers an interest- 

 ing point of view. When you see a butterfly flying leisurely 

 from plant to plant and alighting upon the leaves rather 

 than the blossom, you may be pretty sure that she is bent 

 upon egg-laying. Now watch her to see if she goes at once 



