140 ILLINOIS ACADEMY OF SCIENCE 



male in all cases. He remains by the eggs and appears to 

 protect them well against their ordinary enemies, for when 

 he is removed the eggs quickly dissappear in a few cases 

 observed. They are very probably eaten by crayfish 

 and minnows. Once eight minnows from many that were 

 swarming about the deserted eggs of this species were 

 caught by me. Six were Blunt-nosed Minnows, and two 

 Stone-rollers. No eggs could be found in the digestive 

 tracts of these fish, however, but this may have been due 

 to their complete mastication. At Walnut Lake, Blunt- 

 nosed Minnows were found to be important destroyers of 

 eggs of other species of fish (Hankinson 'OS, p. 204). 



Semotilus atromaculatus (Mitchill). Horned Dace. 



This abundant minnow in this region associates closely 

 with the Stone-roller and like it prefers small creeks to 

 large ones, and it breeds at about the same time and in the 

 same kind of situation, which is a gravel shoal above riffles 

 with a convenient place of refuge. They appear to have a 

 breeding migration, for in the early spring, usually in late 

 March, large individuals are abundant in the Embarrass 

 River, and many are caught by hook then. At other times 

 they are scarce in this stream. Shelf ord ('13, p. 90) notes 

 a prominent up-stream movement for breeding. They 

 usually spawn in April but spawning has been observed by 

 me as late as May 15. The water in which the nests were 

 found varied in depth from 3 to 12 inches (usually 5 or 6 

 inches), and its temperature ranged from 55°F. to 80°F. 



The nest is made by the male fish, which is easily dis- 

 tinguished by the prominent pearl organs on the head and 

 by the more or less intense flushing of red in the breast 

 region. He is usually much larger than other fish of the 

 species on the breeding shoal with him. In this region the 

 nest-building males observed were from about 4 to 8 inches 

 long. Stones are moved as in the case of the Stone-roller 

 but in a more methodical way, since they are carried up 

 stream and dropped in such a manner as to form a distinct 

 ridge (Fig. 3 r. ). There is a pit (Fig. 3, p.) below this 

 ridge where the digging takes place, which forms further 

 and further down stream as the ridge grows longer, the 

 size of the pit remaining about the same. Reighard ('10, 

 p. 1125) has found these ridges 16 or more feet long, but 

 around Charleston they are seldom much more than two 



