XXII. 



SOME SINGULAR THINGS ABOUT CATERPILLARS 



Some one has said that it is the unexpected that 

 always happens. So, to one who may be tolerably 

 familiar with the structure of caterpillars, some 

 new and unexpected feature often presents itself 

 and will then appear in the same or in some modi- 

 fied form through a long series of different species. 

 Or the arrangement or disposition of parts with 

 which he is perfectly familiar may suddenly be 

 found to follow certain laws which he can formu- 

 late but not explain, and which he had before 

 overlooked. 



One of the most fundamental facts in the struc- 

 ture of caterpillars, as of all arthropods, is the 

 repetition of similar parts along the several rings 

 of which the body is composed. But there are in 

 caterpillars, at least, two disturbing elements which 

 modify this law ; one, considering that the meta- 

 morphoses of insects are conceded to be an acquired 

 characteristic, is readily explained, and that is the 



