THE COLORATION OF ANIMALS 



67 



protective efficacy is just the same. This is the case with the Pieridse 

 (Garden Whites). 



All the caterpillars of our Sphingidse, on the other hand, which 

 live on bushes and trees, have on the sides of the segments light 

 oblique stripes, seven in number, which are 

 disposed to the longitudinal axis of the body 

 at the same angle as the lateral veins of a 

 leaf of their food-plant have to the mid-rib. 

 It cannot of course be said that the cater- 

 pillar thereby gains the appearance of a leaf, 

 indeed, if one sees it apart from its food- 

 plant it does not look in the least like a leaf, 

 but among the leaves of a bush or tree this 

 marking secures it in a high degree from dis- 

 covery. Thus the caterpillar of the eyed hawk- 

 moth {Smerinthus ocellatus), when it is sitting 

 among the crowded foliage of a willow, is often 

 very difficult to find, because its large green 

 body does not appear as a single green spot, but 

 is divided by theoblique lateral stripes into sec- 

 tions like the half of a willow leaf, so that even 

 a searching glance is led astray, there being 

 nothing to focus attention on the animal as 

 distinguished from its surroundings (Fig. 3). 

 As a boy I often had the interesting experience 

 of overlooking a caterpillar which was sitting 

 just before me, until after a time I chanced to hit upon the exact spot 

 in the field of vision. 



In the majority of these caterpillars with oblique stripes, the 

 likeness to the half of a leaf is heightened by the fact that the 

 light oblique row is ac- 

 companied by a broader 

 coloured band, suggesting 

 the shade of the leaf's 

 mid-rib. The caterpillar 

 of Sphinx ligustri has a 

 lilac band, and that of 

 Sphinx atropos a blue one. 

 In both cases it is difficult to believe that such striking colours can secure 

 the animals from discovery, yet among the blending shadows of the 

 leaf-complex of their food-plant they greatly increase their re- 

 semblance to a leaf-surface. Of the death's-head caterpillar (Sphinx 



F 3 



Fio. 2. Longitudinally 

 striped caterpillar of a Saty- 

 rid. After EBsel. 



Fie. 3. Full-grown caterpillar of the Eyed 

 Hawk-moth, Smerinthus ocellatus. sh, the subdorsal 

 stripe. 



