Swallow-Tailed Butterflies 159 



is another case where the insect's idea of a sweet 

 odor does not agree with ours ; but maybe it is, as we 

 first hinted, used like a skunk's odor, as a means of 

 defense. 



ICHNEUMONS 



There are a number of flies, and what are called 

 Ichneumons, which have a very annoying and mean 

 way of depositing their eggs upon the surface or 

 under the skin of caterpillars, where the eggs hatch 

 out and feed upon the flesh of their living host. 

 Possibly this vinaigrette carried b}' the striped 

 caterpillar is used to drive aw^ay all such insects as 

 wish to pasture their j^oung upon the body of the 

 live caterpillar, or the smell may even be so dis- 

 agreeable to the toads and the birds as to cause 

 them to refuse to eat the caterpillars. We know 

 the scent is there for some purpose and we know 

 we would not eat one of these caterpillars even if it 

 had no vinaigrette bottles stowed away in a pocket 

 in the nape of its neck, and we also know that when 

 we see a woman bring out a vinaigrette bottle we 

 must not mention parsley " worms," for that would 

 be ungallant. 



These caterpillars are full grown in the fore- 

 part of July and will then measure about an inch 



