THE BREEDING HABITS OF THE RAINBOW 



DARTER (ETHEOSTOMA CCERULEUM 



STORER), A STUDY IN SEXUAL 



SELECTION. 



CORA D. REEVES. 

 Contributions from the Zoological Laboratory of the University of Michigan. No. 113. 



Contents. 



PAGE. 



I. Introduction 35 



II. Usual Appearance, Habitat, and Behavior of the Fish 36 



III. The Breeding Colors, Habitat, and Behavior 38 



IV. Spawning 41 



1. Behavior of a large male toward a female 42 



2. The Spawning attitude 43 



3. The Spawning Act 44 



4. Behavior of two rival males toward each other 45 



5. Behavior of supernumerary males toward the spawning pair 46 



6. Sex recognition 47 



V. Observations bearing on Sexual Selections 47 



VI. Discussion of Results 53 



1. Origin of nest building habit 53 



2. Displays of colors and movements 54 



3. Sexual selection 55 



VII. Summary 57 



VIII. Literature Cited 58 



I. Introduction. 

 The brilliant coloration of the rainbow darter has been fre- 

 quently mentioned since its first description by Storer (1845). 

 It has given the fish its name and its reputation as perhaps the 

 gaudiest of American fresh-water fishes (Jordan and Everman, 

 1896). The bright colors are present, however, only in the male 

 so that there is marked sexual dimorphism. A similar condition 

 exists, so far as I can learn, in all the closely allied forms of 

 darters, each showing a characteristic color pattern. In addition 

 to this the males of each of the many species show in the breed- 

 ing season a more intense coloration. In the spring of 1906 I 

 discovered this Etheostoma breeding under conditions favorable 

 for close observation, and undertook the following study in order 



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