THE CATERPILLAR. 23 



that often we may readily distinguish the thoracic 

 from the abdominal segments without seeing the 

 legs. Thus even in the mere disposition of the 

 spines on a caterpillar^ s back, the future sepa- 

 ration of tliorax and abdomen is foreshadowed., 



It might be supposed that the slightly altered 

 arrangement of the spines in passing from the 

 abdominal to the thoracic tract was due to the 

 larger amount of space on the latter owing to the 

 absence of breathing pores ; but it is wholly inde- 

 pendent of this, for when the spines are well de- 

 veloped on the first thoracic segment, which bears 

 an unusually large spiracle, they align with those 

 of the other thoracic segments and not with those 

 of the abdomen. 



In many caterpillars there is some difference in 

 the relative size of the various segments ; gener- 

 ally speaking, the segment behind the head is 

 rather smaller than the others ; and in one group, 

 the skippers (Urbicolae) 



[Fig. 30], as also in the XJ3 



\s xruw u 1 



goat- weed butterfly [see Fig. Flo . 30.-CaterpUlar of Attytone 



97], it is reduced to such 



a narrow neck as to give the creature a strangled 

 appearance. In another group, on the contrary 

 that to which some of our smallest butterflies 

 belong, the coppers (Yillicantes), blues, and hair- 

 streaks (Ephori) this segment is largely devel- 

 oped, while at the same time the head is smaller 



