114 THE CAUSES WHICH PROPAGATE 



The music, then, appears common to the sexes, and to be 

 produced from the stimulus of love or rivalry, but is perhaps 

 also capable of expressing- fear,. for sometimes a short, clicking 

 noise is made when one of these butterflies is caught in the net. 

 Some other South American Rhopalocera stridulate. Dr. Fritz 

 Miiller relates :—" On October 3Uth, 1876, at the mouth of the 

 Rio Trombudo, a tributary of the Itajahy, I saw two butterflies 

 chasing each other, which produced a loud clicking noise, and 

 settled from time to time in the manner of Ageronia, with 

 the wings expanded horizontally, on dry stems of bamboo."^ 

 I, of course, imagined them to be some species of this genus ; 

 but, after having succeeded in catching one of them, found that 

 it was Eunica Margarita. I may observe the neuration of the 

 wings of that butterfly bears a rather close resemblance to the 

 above, so indeed it may be more nearly allied to that musical 

 genus than is generally assumed. On February 21st, 1877, at 

 the foot of the Serra de Itajahy, I again heard a noise resembling 

 that of Ageronia, but rather louder, produced by two small brown 

 butterflies, which I did not succeed in catching.''^ 



Among the Nymphalidse, or butterflies with only four perfect 

 legs, the African species of Charaxes, perhaps, utter a sound in 

 flight, and several kinds stridulate in repose. The Purple 

 Emperor {Apatura Ilia), when settled on the damj) road or 

 on cow-dung, may be observed to partially expand its wings, 

 and move the fore back over the hind, as if producing a sound ; 

 and the species of Vanessa will often, when disturbed during 

 their characteristic northern hybernation, or during the similar 

 torpidity induced by dull weather or enclosure in the dark, 

 produce, as they sit, a high sand-papery sound, by repeatedly 

 spreading out their wing horizontally, and rubbing the fore- 

 wing's basal portion over the hind, which action and accompany- 

 ing stridor will be repeated on touching the insect's wings, or 

 by merely presenting an object at the performer, evidently 

 indicating the impulse of fear or anger. In this genus colour 

 and music take parallel development, as evinced by one of the 

 most beautiful of stridulators — a welcome annual visitant to the 

 hydrangea and dahlia of our flower-gardens. 



* Tarjnava. 



