BREEDING HABITS OF RAINBOW DARTER. 57 



It would seem that the more brilliant colors are of value to the 

 males possessing them during their combats with other males. 

 But whether the males that succeed in breeding really differ in 

 any definite way in color or color pattern from adult breeding 

 males in general, whether they belong to some one of the many 

 types of coloration, my observations do not show. 



Summary of Observations. 



1. In the adult Etheostoma cceruleum the two sexes are distin- 

 guishable at all seasons of the year because the males have some 

 red and blue in the color pattern while the females are mottled 

 brown. 



2. They usually inhabit the rapid water of small streams. 



3. Out of the breeding season the fish are shy and not easily 

 approached. 



4. The breeding season was observed to extend from April 24 

 to June 2, 1906. 



5. The sexual activity of these darters is limited by tempera- 

 ture and actual spawning was not observed when the water was 

 below 1 5 C. 



6. The colors of the larger males are more brilliant in the 

 breeding season than at other times. The red and especially the 

 blue are greatly intensified and appear on parts of the body on 

 which they are not found during the rest of the year. The adult 

 males show many variations or types of coloration. 



7. The most brilliant colors were found the first of the season, 

 or the last week in April. 



8. The fish at this time congregate on the shallow gravel areas 

 above the rapids. 



9. They lose their shyness and allow close observation with- 

 out showing signs of fear. 



10. The sexes occur in equal numbers but there are always 

 more males than females present on the breeding ground at one 

 time. 



1 1. Among these males certain large brilliant ones have hold- 

 ings which they guard. They may leave these to drive away 

 other males or pursue a female but they return promptly. 



12. The driving away of rival males is by means of display 

 or by blows of the tail or head. 



