1877.] 207 



ON STEIDULATION IN THE GENUS AGERONIA. 

 BY A. ir. SWIXTOIS^. 



That tlie striduktion of these butterflies must be ascribed to the 

 same mechauical cause as we find existing in the genus Vanessa, is not 

 at first obvious ; for whereas the stridulous sounds produced by the 

 latter are emitted generally while the insect is reposing, semi-torpid, 

 and subject to some unusual excitation, the former have only been 

 heard to emit their clicking noise when chasing eaeli other in the free 

 air. Tet there seems no reason on this account to anticipate a 

 different mode of production, as I have observed that the Vanessce will 

 emit the sound on the wing as well as when at rest, motion of the 

 wings being the only requisite for its production. 



Darwin notices the sounds made by Ageronia Fero7iia (Voyage of 

 the Beagle, iii, pp. 37-8) thus: "Brazil, May- June, 1832.— This 

 butterfly is not uncommon, and generally frequents the orange groves. 

 Although a high flier, yet it very frequently alights on the trunks' of 

 trees. On these occasions, its head is invariably placed downwards, 

 and its wings are expanded in a horizontal plane, instead of being 

 folded vertically, as is commonly the case. This is the only butterfly 

 which I have ever seen that uses its legs for running. But a far more 

 singular fact, is the power which this species possesses of making a 

 noise. Several times when a pair, probably male and female, were 

 chasing each other in an irregular course, they passed within a few 

 yards of me, and I distinctly heard a clicking noised Darwin is cor- 

 roborated by Mr. A. E. Wallace (Trans. Ent. Soc, n. s. ii, 257) : 

 "The common species (at Para), Ageronia Feronia, produces it (the 

 sound) remarkably loud, when two insects are chasing each other and 

 constantly striking together. One alone does not produce the sound 

 in flying, and I have never heard it made by the small species, 

 A. Cliloe, which is equally common with the other. I am inclined, 

 therefore, to believe that it is produced in some way by the contact of 

 two insects, and that only the larger and stronger- winged insects can 

 produce it."* 



Mr. E. Doubleday (Trans. Ent. Soc, iv. Proceed., p. 123) says 

 that " he had examined Peridromia Feronia, the butterfly described by 

 Mr. C. Darwin as making a noise during flight like the rustling of 

 parchment, and that he had detected a small membranous sac at the 



(M.J B. Capronnier (Ann. Soc. Ent. Beige, xvii, p. 21) says of Ageronice — "There have 

 hitherto been some doubt.s. if the noise referred to was peculiar to the male, but M Van Vol.xem, 

 who ha.s had frequent opportunities of observing the Agcruuin enjoying their frolics, affirms that 

 the noise is common to both sexes. — Eds. ] 



