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BRANCH ARTHROPODA 



insects and of other animals is indirectly due to two causes: 

 first, the advantages given to the individual or species in the 

 struggle for existence by these specific colors and color-patterns, 

 which as in the case of the gray moth on the tree-trunk or 

 the katy-did among the green leaves helps to conceal them 



Fig. 88. Larva of regal walnut moth (Cithero'nia rega'lis) extended (two- 

 thirds nat. size). (Photographed from life.) 



from their enemies by affording protective resemblance, or as 

 in the case of the bumble-bee or the milkweed butterfly to 

 warn the enemy of the danger of sting or of the disagreeable odor 

 and taste. The advantage gained is easy to be seen in each 



Fig. 89. Pupa of regal walnut moth (three-quarters nat. size). (From 



life.) 



case. They believe that these particular color-patterns are 

 due, in the second place, to gradual development " through 

 natural selection of naturally occurring, advantageous varia- 

 tions." 



The direct cause of color may be chemical, depending on the 



