94 BUTTERFLY SOUNDS 



one of them a cavity on the under side of the 

 upper wing near the region of the costal nervure, 

 and another in the swollen part of the costal ner- 

 vure of the same wing, both of them parts not 

 covered by the hind wings in flight. He rightly 

 disclaims any attempt to discover "a connection 

 between either of these peculiarities in structure 

 and the sound produced by the insect." Mr. 

 Swinton, however, in several places has attempted 

 to show that the base of the anal veins of the front 

 wing in the stridulous Vanessini and in Ageronia 

 has a certain structure comparable to a file or 

 lima, parallel indentations or shght striae being seen 

 across its surface under a strong magnifying power. 

 But this explanation can in no way answer, be- 

 cause an exactly similar feature may be found in 

 all the other veins of all these butterflies, there 

 being nothing distinctive in the veins themselves, 

 either in the front or hind wing, in the regions 

 which naturally overlap. When one examines, 

 however, the Vanessini of the temperate regions, 

 he will discover that the hind wings are in many 

 cases furnished not only with scales but with long, 

 pointed bristles, and I at first thought that these 

 bristles might be the cause of the sounds, although 

 they seemed to be just as abundant in other parts 



