BUTTERFLY SOUNDS. 395 



four iucliecj uf my uosc, and then suddenly whisking oft' with a distinct 

 click at turning. 



All the instances thus far gi\'en relate to the family Nymphalidae, and 

 therefore the following instance recorded by Rev. A. E. Eaton of England, 

 is of unusual interest. He states (Ent. monthl. mag., xix : b^>) that he 

 heard Parnassius apollo make a rustling noise by "slowly Happing her 

 wings" while clinging to a ftower, " and scraping the hinder pair with 

 her four posterior legs, which were thrust backwards simultaneously each 

 time that the wings o})ened " ; it continued to do this even after the frout 

 wings were firmly held, but stopped when the hind wings were seized. 



The only persons who seem to have endeavored to discover the cause of 

 these sounds are the late Mr. Doubleday and Mr. Swinton. Mr. Double- 

 day examined the species of the genus Ageronia in the British Museum in 

 vain for any sufticient cause drawn from the external structure of the ani- 

 mal. He found certain peculiarities, one of them a cavity on the under 

 side of the u[)per wing near the region of the costal nervure, and another 

 in tiie swollen part of the costal nervure of the same wing, both of them 

 parts not covered by the hind wings in ftight. He rightly disclaims any 

 attempt to discover " a connection between either of these peculiarities in 

 structure and the sound produced by the insect.'" ^Ir. Swinton, however, 

 in several places has attempted to show that the base of the anal veins of 

 the front wing in the stridulous Yanessidi and in Ageronia has a certain 

 structure comparable to a file or lima, parallel indentations or slight striae 

 being seen across its surface under a strong magnifying power. But this 

 ex})lanation can in no way answer, because an exactly similar feature may 

 be found in all the other veins of all these butterfties, there beintj nothinof 

 distinctive in the veins themselves, either in the front or hind wing, in the 

 resrions which naturallv overlai). When one examines, however, the 

 Yanessidi 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 l)e the cause of the 

 sounds, although they seemed to be just as abundant in other parts of the 

 wing as in those which were naturally covered by the op])osite wing. Not 

 having at my disposition any specimens of Ageronia at the time these ob- 

 servations were made, 1 re(juested Mr. Butler of tlie British Museum to 

 examine the wings of Ageronia : but he found upon them no bristles 

 whatever. If, however, one will examine the surfaces In'ought into con- 

 tact between the two wings in the insects known to produce audible sound, 

 he will note that nearly all the scales on the under surface of the front 

 wing and those on the u})per surface of the hind wing next the base, that 

 is, in just those portions of the wing which overlap each other, are innch 

 suifiJIer a)n1 more erect than in any other part of tlic wing, even than 

 those in the immediate vioinitv, and liv experiment can show that when 



