THE LEPIDOPTERA 299 



The caterpillar when full-grown (Fig. 31 la and 6) is about two inches 

 long, green with a black cross band on each segment, which may enclose six 

 yellow spots or may fail to close these in on the front side of the band. 

 Just back of the head is an opening out of which a soft, widely forked 

 horn can be protruded when the insect is distributed. Such structures 

 are called osmeteria and give off a disagreeable, pungent odor, and are 

 probably to drive away enemies which may attack them. 



This insect is rarely if ever important enough to call for any control 

 other than destroying the larvae by hand, though in most cases spraying 

 with a stomach poison would be entirely effective if such a treatment were 

 needed. 



A similar species present on the Pacific Coast, has the same habits. 



