6 JACOB REIGHARD. 



3. Coloration and Color Changes. The mature white sucker, 

 when seen in its native waters or in captivity, is ordinarily uni- 

 formly olivaceous on the back and sides and white below. There 

 is no color pattern nor are there color differences between the 

 sexes. The suckers seen from the bridge (Fig. 4) were so different 

 in coloration from all that I had seen before, that I was at first 

 doubtful as to their identity. Each had a broad yellow-white 

 stripe which crossed the occiput and extended thence down the 

 sides. When some of these fish were seined they were found to 

 have the usual uniformly olivaceous color. They were placed 

 in an aquarium, males and females together, and four hours 

 later the males had begun to move about and to feed. Shortly 

 afterward the light stripe appeared across the occiput and down 

 the sides. Beneath the light stripe was a broad dark stripe 

 (Fig. 4) and in one of the males this had a rosy tinge. During 

 the actual pairing described below, the rosy tinge gave place to a 

 brilliant crimson. Later I often saw the light stripe appear in a 

 few seconds on uniformly colored males that were on the rapids. 

 This happens regularly in the breeding season when the sexes are 

 together. 



4. Sexual Differences. It is at first difficult to discriminate 

 between males and females. As seen from the bridge the paired 

 fins are transparent white in both and in both the yellowish 

 white stripe crosses the occiput and extends down the sides. 

 But the males are on the average smaller than the females and 

 slenderer. It is soon apparent that the occipito-lateral stripe is 

 whiter in them and that their backs may be flecked with white 

 especially between the dorsal fin and the occiput (Fig. 4, male 

 at right of female). In the region of the occiput the white 

 flecks may form a distinct patch which, seen from a distance, 

 looks like fungus. The white flecks are perhaps not always 

 present in males, but I have never seen them in females. In 

 pairing males, seen in the aquarium, the dorsal half of the eye is 

 lighter colored than in females, but I do not know that this is 

 not the case at other times. The differences so far noted afford 



C. commersonii and one of the other species, probably C. catosiomus, were seen in 

 the spawning attitude. The fish were not disturbed when a boat, in which were 







two children and a barking dog, was poled about above them so that they were 

 not more than five feet from it. 



