Jo8 The Descent of Man. Part II. 



Sornu mcitlis also produce sounds ; for instnnce, the males of 

 ThtaiXjhora fuvra. On two occasions Mr. F. Buchanan White' 

 heard a sharja quick noise made by the male of Hylophila 

 prasinana, and which he believes to be produced, as in Cicada, 

 by an elastic membrane, furnished with a muscle. Ho quotes, 

 also, Giienee, that Setina produces a sound like the ticking 

 of a watch, apparently by the aid of " two large tympauiform 

 " vesicles, situated in the pectoral region ; " and these " are much 

 " more developed in the male than in the female." Hence the 

 Rnund-producing organs in the Lepidoptera appear to stand in 

 some rcirtion with the sexual functions. I have not alluded 

 to the weii-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 odour, 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 

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

 colours 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 

 variations been accumulated and determined as a protection, 

 or for some unknown purpose, or that one sex may be at- 

 tractive to the other? And, again, what is the meaning of the 

 colours 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 b- given. 



With our beautiful English buttei'flies, the admiral, peacock, 

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

 are alike. This is also the case with the magnificent Heliconidse, 

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

 tropical groups, and in some of our English butterflies, as the 

 purple emperor, orange-tip, &c. (Apatara Iris and Anthocharia 

 cardamines), the sexes differ either greatly or slightly in colour. 

 No language suffices to describe the splendour of the males of 



Srd, 1845, f Z23) a peculiar i"'^m- observations, 'The Scottish Natural- 



branous sac at the base of the ist,' July 1872, p. 214. 



front wings, which is probably con- ' ' The Scottish Naturalist,' Julj 



nected with the production of i.ie 1872, p. 213. 



aouud. For the ca">e of T..«cophora, * ' Zoological Fecord,' 1869., p 



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



401. For Jlr. Buchanan White'* 



