BUTTERFLIES AND MOTHS. 305 



toothed wheel passing under a spring catch, and which can be 

 heard at the distance of several yards: I noticed this sound at 

 Rio de Janeiro, only when two of these butterflies were chasing 

 each other in an irregular course, so that it is probably made dur- 

 ing the courtship of the sexes.^ 



Some moths also produce sounds; for instance, the males of 

 Thecophora fovea. On two occasions Mr. F. Buchanan White^ 

 heard a sharp quick noise made by the male of Hylophila pras- 

 inana, and which he believes to be produced, as in Cicada, by an 

 elastic membrane, furnished with a muscle. He quotes, also, 

 Guenee, that Setina produces a sound like the ticking of a watch, 

 apparently by the aid of "two large tympaniform vesicles, sit- 

 "uated in the pectoral region;" and these "are much more 

 "developed in the male than in the female." Hence the sound- 

 producing organs in the Lepidoptera appear to stand in some re- 

 lation with the sexual functions. I have not alluded to the well- 

 known noise made by the Death's Head Sphinx, for it is generally 

 heard soon after the moth has emerged from its cocoon. 



Girard has always observed that the musky odor, which is 

 emitted by two species of Sphinx moths. Is peculiar to the males;' 

 and in the higher classes we shall meet with many instances of 

 the males alone being odoriferous. 



Every one must have admired the extreme beauty of many but- 

 terflies and of some moths; and it may be asked, are their colors 

 and diversified patterns the result of the direct action of the 

 physical conditions to which these insects have been exposed, 

 without any benefit being thus derived? Or have successive va- 

 riations been accumulated and determined as a protection, or for 

 some unknown purpose, or that one sex may be attractive to the 

 other? And, again, what is the meaning of the colors being 

 widely different in the males and females of certain species, and 

 alike in the two sexes of other species of the same genus? Before 

 attempting to answer these questions a body of facts must be 

 given. 



With our beautiful English butterflies, the admiral, peacock, 

 and painted lady (Vanessse), as well as many others, the sexes are 

 alike. This is also the case with the magnificent Heliconidae, ana 

 most of the Danaidae in the tropics. But in certain other tropical 

 groups, and in some of our English butterflies, as the purple em- 



= See my 'Journal of Researches,' 1845, p. 33. Mr. Doubleday ha3 de- 

 tected ('Proc. Ent. Soc' March 3rd, 1845, p. 123) a peculiar membranous 

 sac at the base of the front wings, which is probably connected with 

 the production of the sound. For the case of Thecophora, see 'Zoo- 

 logical Record,' 1869, p. 401. For Mr. Buchanan White's observations, 

 'The Scottish Naturalist,' July 1872, p. 214. 



3 'The Scottish Naturalist,' July 1872, p. 213. 



4 'Zoological Record,' 1869, p. 347. 



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