THE BUTTERFLY. 



composed of the abdomen, though in the female 

 when heavy with eggs it will often doubly out- 

 weigh the parts in front ; externally, however, it 

 is the least interesting part of the body. It is 

 composed of eight simple rings covered with 

 scales, variegated, if at all, only by stripes or 

 series of dots, and bearing upon the sides of the 

 first seven segments a pair of spiracles entirely 

 concealed by scales. As in other insects, one 

 finds at the extremity pieces of very variable con- 

 struction, which here, more perhaps than else- 

 where, have the appearance of forming parts of 

 still other rings ; they are, however, only append- 

 ages of the last and the penultimate segments ; 

 this is proved by what is 

 known of their origin and 

 mode of growth in other in- 

 sects, where they often have 

 an extraordinary development, 

 as ovipositors or stings in one 

 sex or as nippers in the other. 

 They are entirely new struc- 

 tures, arising in the pupal 

 stage, first as mere tubercles, 

 then as outgrowths from the 

 inferior plates of the body, but 

 afterward becoming attached to various portions 

 of the last two segments, in such a way as to 

 allow them a certain freedom of motion, and often 



FIG. 77. Asymmetrical 

 appendages of the right 

 and left sides of the abdo- 

 men in Thanaos Eiinius, 

 X 10. 



