ORGANIC EVOLUTION 



Amazon region, Bates says : " It is almost always the males 

 only which are beautiful in colors." (See also Plates 31 

 and 33, A.) 



The males of many kinds of fishes are more brilliantly 

 colored than the females, and in some species the males 



have ornamental ap- 

 pendages which are not 

 found, or are less de- 

 veloped, in the females 

 (Plate 32). Apparently 

 these characters are to 

 be referred to sexual 

 selection, for the colors 

 are generally more 

 brilliant at the breeding 

 season, and the behavior 

 of the male in the pres- 

 ence of the female is 

 such as to show off to 

 the best advantage the 

 brightly colored parts 

 of his body, or the orha- 

 D mental appendages. 



In some of the Am- 

 phibia the males are 

 more conspicuous than 

 the females during the breeding season. Darwin says, in 

 his Descent of Man: "With our common newts (Triton 

 punctatus and cristatus) a deep, much indented crest is 

 developed along the back and tail of the male during the 

 breeding season, which disappears during the winter (Plate 



FIG. 7. Heads of male and female beetles. The 

 left-hand figures show the males. [After DARWIN.] 



A. Copris isidis. B. Phanasus faunus. 

 cus cantori, D. Onthophagus rangifer. 



C. Dipeli- 



