Chap. XL BUTTERFLIES AND MOTHS. 387 



between the butterflies of Borneo says, "They whirl 

 " round each other with the greatest rapidity, and appear 

 " to be incited by the greatest ferocity." One case is 

 known of a butterfly, namely the Ageronia feronia, 

 which makes a noise like that produced by a toothed 

 wheel passing under a spring catch, and which could be 

 heard at the distance of several yards. At Kio de Janeiro 

 this sound was noticed by me, only when two were 

 chasing each other in an irregular course, so that it is 

 probably made during the courtship of the sexes ; but I 

 neglected to attend to this point. 2 



Every one has admired the extreme beauty of many 

 butterflies and of some moths ; and we are led to ask, 

 how has this beauty been acquired ? Have their colours 

 and diversified patterns simply resulted from the direct 

 action of the physical conditions to which these insects 

 have been exposed, without any benefit being thus de- 

 rived ? Or have successive variations been accumulated 

 and determined either as a protection or for some un- 

 known purpose, or that one sex might be rendered 

 attractive to the other ? And, again, what is the mean- 

 ing of the colours being widely different in the males 

 and females of certain species, and alike in the two 

 sexes of other species? Before attempting to answer 

 these questions a body of facts must be given. 



With most of our English butterflies, both those which 

 are beautiful, such as the admiral, peacock, and painted 

 lady (Vanessse), and those which are plain-coloured, 

 such as the meadow-browns (Hipparchiae), the sexes 

 are alike. This is also the case with the magnificent 

 Heliconidse and Danaidse of the tropics. But in certain 



2 See my ' Journal of Eesearches,' 1845, p. 33. Mr. Doubleday has 

 detected (' Proc. Ent. Soc.' March 3rd, 1845, p. 123) a peculiar mem- 

 branous sac at the base of the front wings, which is probably con- 

 nected with the production of the sound. 



2 c 2 



