200 SOME SINGULAR THINGS 



siveness. Possibly this will explain many other 

 cases. 



If we examine the arrangement of the spiracles 

 upon the sides of the body, we shall find that the 

 first thoracic and the last abdominal pair are in- 

 variably much larger than the others, which are 

 equal among themselves. The ex]3lanation of this 

 is easy. The respiratory tube of each has to feed 

 a very much larger field, the head and second tho- 

 racic segments being fed by the tubes finding their 

 outlet at the first thoracic segment, and several of 

 the hinder abdominal segments of the body being 

 equally dej)endent upon that of the eighth abdom- 

 inal segment. The spiracle of the first thoracic 

 segment is also situated on a higher level than the 

 ordinary abdominal spiracle, and this is a conse- 

 quence, in part at least, of the ordinarily smaller 

 size of this segment ; yet it is also true in those 

 forms in which the first thoracic segment is greatly 

 enlarged. But what is curious is that in certain 

 groups, the Lycaeninae in particular, and the 

 Hesperidae to a less extent, the spiracle of the 

 eighth abdominal segment is also situated at a con- 

 siderably higher level than those of the other 

 abdominal segments. This seems another instance 

 of the polar arrangements of parts to which we 



