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Show 190 MR. G. F. HAMPSON ON STRIDULATION [Mar. 1, upper surface, and I suggest that the longitudinal fold acts as a channel for the tarsus, the ridges on each side striking against the spines. Mr. E. Meyrick informs m e that this insect makes a loud buzzing sound during flight, and the first time he heard it he thought a " humble-bee" was buzzing round his hat; he tells m e that the insect during flight swings rapidly up and down in the air, and he thought the vibration of the air on the membrane might account for the sound. The only other Lepidoptera known to make a similar clicking Fig. 2. Hecatesia fenestrata, Boisd. 3. Fore wing. sound are some of the species of Ageronia, e. g. A. feronia, fornax, amphinome, and arethusa, as was first discovered by Darwin during the voyage of the ' Beagle,' and confirmed by Wallace, and again by Fritz Miiller, w ho says that he also observed it in Eunica margarita and a small brown butterfly which he could not capture. Darwin says that when a pair of Ageronia feronia were chasing each other they produced a clicking sound similar to that produced by a toothed wheel passing under a spring catch, and that the noise was produced at short intervals and was audible at twenty yards' distance. Wallace says the noise was never produced by a single specimen, but only when a pair were chasing each other, and he imagined it was in some way produced by the contact of the two insects; but Bigg-Wither noted that the butterfly settled head downwards with its wings outspread, and that if approached it raised its wings sharply once or twice, producing a whip-like sound, and that it also made the same sound while on the wing. Ed. Doubleday examined the butterfly, and found a small membranous sac between the costal and subcostal nervures of the fore wing, with a structure along the subcostal nervure like an Archimedean screw; he very properly disclaimed this structure being necessarily connected with the sound, and, as Scudder pointed out, these are merely the swollen base of the subcostal nervure found in so many Nymphalince and the tracheal vessel in the nervure. Swinton says that the sound is produced by the costal nervure of the hind wing, which is ridged like a file, being received into and rubbing against a small depression of the fore wing ; but, as Scudder |
