The Origin of the Markings of Caterpillars. 321 



bility of being able to ascribe any biological value 

 to this character, which appeared to me only 

 conspicuous, and not protective. Cases may actually 

 occur in which the brightly coloured edges of the 

 oblique stripes make the caterpillar conspicuous 

 just in the same manner as any marking may bring 

 about a conspicuous appearance by presenting a 

 striking contrast of colour. I am acquainted with 

 no such instance, however. As a rule, in all well- 

 adapted caterpillars, considering their colour in 

 its totality, this is certainly not the case. The 

 coloured edges, on the contrary, enhance the 

 deceptive appearance by representing the oblique 

 shadows cast by the ribs on the under-side of the 

 leaf ; all these caterpillars rest underneath the 

 leaves, and never on the upper surface. 



This explanation may, perhaps, at first sight 

 appear far-fetched, but if the experiment be made 

 of observing a caterpillar of Sphinx Ligustri on 

 its food-plant, not immediately before one's eyes 

 in a room, but at a distance as under natural con- 

 ditions, it will be found that the violet edges do not 

 stand out brightly, but show a colour very similar to 

 that of the shadows playing about the leaves. The 

 coloured edges, in fact, produce a more effective 

 breaking up of the large green surface of the 

 caterpillar's body, than whitish stripes alone. Of 

 course if the insect was placed on a bare twig in 

 the sun, it would be easily visible at a distance ; the 

 larva never rests in such a position, however, 



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