100 CONTROLLED NATURAL SELECTION 
protection; the absence of scent in many 
hen birds which nest on the ground, in- 
dicates that scent plays a greater part in 
Nature than our feeble sense organ would 
lead us to imagine. 
The pleasant perfume which some male 
insects have, may be to draw an enemy’s 
attention to them, during copulation, rather 
than to the female. In offensively scented 
insects, the sexes are usually similar, and 
the character is probably of a warning 
nature. 
This concludes the majority of the char- 
acters of conspicuousness which distinguish 
parents from young, male from female: in 
the one case, young as protected at the ex- 
pense of parents; in the other, females at 
the expense of males. The following table 
indicates how precisely similar are the 
methods used; examples are given from 
among birds: 
