V. WARNING COLORS, TERRIFYING MARK- 

 INGS, AND OTHER PROTECTIVE DE- 

 VICES, WITH EXAMPLES 



Wallace's Theory of Warning Colors 



UNTIL the time of Wallace, the gaudy colors of 

 caterpillars were a most perplexing problem. Dar- 

 win found that his law of sexual selection could not 

 act in the case of sexless caterpillars. Wallace 

 reasoned in this way: "Applying here the analogy of the 

 other insects, I reasoned that since some caterpillars were evi- 

 dently protected by their imitative coloring, and others by 

 their spiny or hairy bodies, the bright colors of the rest must 

 also in some way be useful to them. I further thought that 

 as some butterflies and moths were greedily eaten by birds, 

 while others were distasteful to them, and these latter were 

 mostly of conspicuous colors, so probably these brilliantly 

 colored caterpillars were distasteful and therefore never eaten 

 by birds. Distastefulness alone would, however, be of little 

 service to caterpillars, because their soft and juicy bodies are 

 so delicate that if seized and afterwards rejected by a bird, 

 they would almost certainly be killed. Some constant and 

 easily perceived signal was therefore necessary to serve as a 

 warning to birds never to touch these uneatable kinds, and 

 a very gaudy and conspicuous coloring with the habit of fully 

 exposing themselves to view becomes such a signal, being in 

 strong contrast with the green and brown tints and retiring 

 habits of the eatable kinds." ^ 



Weir in England showed by experiments of feeding larvae to 

 birds, that hairy and spiny caterpillars were uniformly rejected 

 by all his ten species of captive birds. In the case of the tortoise 



^ "Natural Selection and Tropical Nature," p. 83. 

 137 



