BREEDING HABITS OF RAINBOW DARTER. 4 1 



proach or lying so still as to escape notice, they now make no 

 effort at concealment. It is often possible by nearing the stream 

 slowly to reach the margin without frightening them. They 

 quickly become accustomed to one's presence and are then not 

 disturbed by one's wading among them. I have touched them 

 with my boot tips or stroked them with a small wire without 

 their moving. It is then possible to stand directly over them 

 and even to examine them with a hand lens without in any way 

 modifying their normal behavior. They appear to swim here and 

 there at random. 



The breeding areas so swarm with them that, one day, I counted 

 twenty-six in a single square yard. Since the females are so in- 

 conspicuously colored as to be easily overlooked, there may have 

 been more fish in that space. There always seemed to be more 

 males than females present on the spawning ground. Early in 

 the season I estimated four or five to one, and among my notes 

 for June I is the item, "Seven darters in sight ; only one female." 

 This proportion continued for several days but collections of fish 

 made in November did not show this inequality in the number 

 of the two sexes. It therefore appears that the larger number 

 of males on the breeding grounds depends on the difference in 

 the habits of the two sexes as is shown below. 



IV. The Spawning. 



Although all the fish seem to be moving about over the 

 spawning area promiscuously, close watching shows that this is 

 true only of the females and small males. On the other hand, 

 there are some of the large brilliant males which remain each 

 within a restricted area which he guards and from which he drives 

 the other males. Among such males it often happens that a 

 single individual may be distinguished by peculiarities of colora- 

 tion and may thus be kept under observation for hours at a time. 

 The plots guarded by individual males we may call their " hold- 

 ings." The width of these holdings does not usually exceed 

 fifteen inches but as the length varies from fifteen inches to two 

 feet they may include more than two square feet. A male may 

 leave his holding to pursue a female or he may go beyond it 

 while he energetically drives away another male, but in either 



