138 NATURE SKETCHES IN TEMPERATE AMERICA 



shell and peacock butterfly larvae, they were rejected, not on 

 account of the hairs and spines, but because they are distasteful. 

 The young caterpillars in which no hairs were developed, as 

 well as the smooth pupae of the foregoing species, were refused 

 as persistently as the spined larvae. Hairs and spines here 

 would seem to be mere signs of uneatableness. 



Similarly, smooth, gayly colored caterpillars which never con- 

 ceal themselves, but on the contrary appear to court observa- 

 tion, were subject to experiment. One species of these larvae 

 was pale yellow with a broad blue or green lateral band; another 

 was greenish white with yellow bands and black spots, etc. 

 These were given to the birds at various times, sometimes 

 mixed with other kinds of larvae which were greedily eaten, 

 but they were in every case rejected, apparently unnoticed, 

 and were left to crawl about till they died. 



Lastly, dull-colored and i)rotected larvae were used in the 

 observations, and the results of numerous experiments by Weir 

 and given by AVallace are as follows: "All caterpillars whose 

 habits are nocturnal, which are dull colored, with fleshy bodies 

 and smooth skins, are eaten with the greatest avidity. Every 

 species of green caterpillar is also much relished. All Geome- 

 tridae whose larva* resemble twigs as they stand out from the 

 plant on their anal prolegs, are invariably eaten." 



Other experiments of this nature have been made with lizards, 

 frogs, and spiders, and Wallace was convinced that his theory 

 of warning colors had received substantial support, for he 

 says: "I tiiink, fairly claim, this is a case in which the power of 

 prevision has been successfully exerted, and therefore as furnish- 

 ing a very powerful argument in favor of the truth of natural 

 selection." 



By referring to the part on the Saddle Back Larva, an 

 excellent example of warning colors is shown. 



It is the same theory of warning coloration, applied to cater- 

 pillars by Wallace, which is supposed to act in preserving the 

 conspicuous and often brightly colored butterflies from attacks 

 by predaceous animals. These insects possess to a large extent 

 ill-tasting blood lymph or some specially secreted acrid sub- 

 stances that birds dislike. By the possession of these unsavory 

 characters, the color pattern of the animals possessing them 



