Variation and Natural Selection. 85 



and chrysalids reared from the same brood will vary accord- 

 ing to the colour of their surroundings. 



If this process of protective resemblance be carried far, 

 the general resemblance in hue may pass into special 

 resemblance to particular objects. The stick-insect and 



Fig. 18. Caterpillar of a moth (Ennomos tiliaria) on an oak-spray. (From 

 an exhibit iu the British Natural History Museum.) 



the leaf-insect are familiar illustrations, though no one 

 who has not seen them in nature can realize the extent of 

 the resemblance. Most of us have, at any rate, seen the 

 stick-caterpillars, or loopers (Fig. 18), though, perhaps, few 



