Chap. XI. 
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 Rio 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 (Yanessse), and those which are plain-coloured, 
such as the meadow-browns (Hipparchise), the sexes 
are alike. This is also the case with the magnificent 
Heliconidae and Danaidm of the tropics. But in certain 
2 See my 1 Journal of Researches/ 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 
