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 birds. 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. 
%8. 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 3 
sexes are about equal innum- Fie. 70.—Torpedo or electric ray (War- 
hers, ‘Where mating exists, ik brasiliensis), showing electric 
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 
