116 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. SS.— Larva of rciial walnut iiidtli {('itluro'nui nija'Us) cxtcmled (two- 

 thirda nal. sizt_0- (rhotographud 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 

 Ufe.) 



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 



