54 



HEREDITY AND SELECTION IN SOCIOLOGY 



could also be cited. The hind-wing of this butterfly is for about 

 three-quarters of its size deep black, and for about one-quarter 

 yellow. When the animal is at rest, this wing is covered by the 

 fore-wing. The latter is of reddish-brown colour sprinkled with 

 black, and with a black pattern on it resembling with extra- 

 ordinary precision the venation of a leaf. A perpendicular line 

 commences at the end of the wing, and breaks off a little more 

 than half-way along, and three black lines flank the perpendicular 

 one on either side (Fig. 4). After breaking o£E in the centre of 

 the wing, the perpendicular line begins again, but is shadowy 



Fig. 4. — Fore-wing op Phyllodes oenata, showing Pattern composed 

 cm A Pbependicuiae Line and Three Black Lines on either 

 Side. 



and indistinct, as are also its flanking lines. The insect, when 

 at rest, exactly resembles a withered leaf, and it must be im- 

 possible to distinguish it from the leaves among which it hves. 

 This is a case of adaptation to the conditions of the environ- 

 ment. The colouring of the fore-wing of Pliyllodes ornata pos- 

 sesses biological value for that species, enabling it to escape 

 detection by its enemies. Natural selection has here been at 

 work, for those insects whose fore- wing was less perfectly adapted 

 to the colour of the surrounding leaves were more likely to be 

 detected and destroyed, and thus it has come about that, 

 as only those individuals which were best adapted survived. 



