ADAPTATIONS 



135 



ous coat is very thick and serves to protect them effectu- 

 ally. This is especially true of the beetles. Some insects 

 are inedible (as mentioned in Chapter XII), and are con- 

 spicuously colored so as to be readily recognized by in- 

 sectivorous bird^. The birds, knowing by experience that 

 these insects are ill-tasting, avoid them. Others are ef- 

 fectively concealed from their enemies by their close 

 resemblance in color and marking to their surroundings. 

 These protective resem- 

 blances are discussed in 

 Chapter XII. 



78. Adaptation for rivalry. 

 In questions of attack and 

 defense, the need of meeting 

 animals of their own kind as 

 well as animals of other 

 races must be considered. In 

 struggles of species with 

 those of their own kind, the 

 term rivalry may be applied. 

 Actual warfare is confined 

 mainly to males in the breed- 

 ing season and to polyga- 

 mous animals. Among those 

 in which the male mates 

 with many females, he must 

 struggle with other males for 

 their possession. In all the 

 groups of vertebrates the 

 sexes are about equal in num- 

 bers. Where mating exists, 

 either for the season or for 



life, this condition does not involve serious struggle or 

 destructive rivalry. 



Among monogamous birds, or those which pair, the 

 male courts the female of his choice by song and by display 



FIG. 70. Torpedo or electric ray (Nar- 

 cine brasiliensis), showing electric 

 cells. 



