ABOUT CATERPILLARS 199 



symmetrical polarity seems quite akin to what I 

 once pointed out in the markings of the wings of 

 butterflies, where corresponding ocelli are found 

 upon the wings in antithetic positions as related to 

 the vein structure beneath. Another instance of 

 this polarity is seen in many of the caterpillars of 

 the Satyrinae, in all of which the terminal segment 

 ends in a fork of greater or less dimensions, in 

 some instances taking the form of a long, pointed 

 spine on either side, directed backward. When 

 this is the case, and especially when it is most 

 developed, the head also is crowned with a similar 

 pair of pointed spines, and at rest the head is bent 

 downward, so that these spines are thrown forward 

 and the body ends at each extremity in a pair of 

 long pointed spines. In this instance, at least, a 

 purpose might be seen in such an armature, for it 

 would appear as if the head bearing these long 

 pointed spines would present a formidable appear- 

 ance to some of its enemies, especially as it is able 

 to present these organs at any point with great 

 force and rapidity. If an enemy, alarmed at the 

 front aspect, sought to assail the creature in the 

 rear and were to find a similar pair of spines, it 

 might well be conceived that he would presume 

 that these also could be used with equal offen- 



