BUTTERFLY-HUNTING BEGINS. 37 



tage, and to attract the other by its own 

 beauty. If a third and prettier butterfly 

 happens to sail up, the belle will bestow her 

 affections upon the new-comer, and the 

 vanquished beau will slink away disgraced, 

 leaving her to her chosen mate. This second 

 sort of selection is going on for ever, side by 

 side with the first ; the prettiest, freshest, and 

 most daintily-marked insects being always 

 preferred in the pairing over duller, dingier, 

 or more battered rivals. 



It is interesting also to note how the two 

 kinds of selection run parallel with one 

 another. While the butterflies are poised 

 motionless upon twigs or flowers they are in 

 the greatest danger from birds ; but in such 

 positions they close their wings and display 

 only the outer surface, which is imitatively 

 and protectively coloured. The constant 

 picking off of all those which can be distin- 

 guished when at rest suffices to keep the pro- 

 tective colours always true. On the other 

 hand, when the insects are on the wing, 



