ABOUT CATERPILLARS 203 



is quite unknown. That tliey may be odoriferous 

 seems higlily improbable, for, though we can easily 

 conceive that their insect enemies might perceive 

 an odor from them, did such exist, which would be 

 imperceptible to our senses (as we have the best 

 reason for believing is the case with minute 

 odoriferous organs of the perfect insect), yet we 

 have not a particle of evidence to this effect, since 

 in not a single instance have we been able to per- 

 ceive any odor whatever from them. In the case 

 of the organs of the mature forms, we conclude 

 them to be odoriferous because in a few instances 

 we can perceive an odor, and may fairly argue that 

 entirely similar structures in others from which we 

 can perceive no odor emit, nevertheless, some scent. 

 Such evidence is absolutely wanting with regard to 

 the present structures, and their use is therefore a 

 subject for research. On experimenting, however, 

 with some of the caterpillars of Pierinae which bear 

 them when full grown, I have found the globule at 

 the summit to be visibly increased when the crea- 

 ture was disturbed. 



There is still another structure only recently 

 made known, the purpose of which is obscure. 

 These are the crateriform, chitinous annuli, which 

 are ranged in longitudinal rows along the abdomi- 



