FIELD BOOK OF PONDS AND STREAMS 



Two similar species of miller's thumbs, Cottus hairdii (Fig. 

 283), and Cottus cognatus, are common in clear, rocky brooks 

 and lakes. Although they most commonly hide on the stony 

 bottom they are also frequently found in tangles of stonewort 

 and pondweed. They feed upon insects, small crustaceans 

 and algae; occasionally they eat the eggs of other fishes. 



They spawn through April to July. The eggs are salmon- 

 colored, about one-eighth of an inch in diameter, and laid in 

 a grape-like cluster of a hundred or two, glued to the under 

 sides of stones in shallow water, where there is more or less 

 current. The male seems to select the site, while the females 

 tarry about. Later one of them joins the male and then 

 deposits her eggs. He loiters near the eggs protecting them 

 until they hatch. 



Size. — Small, up to 5 to 6 inches. 



Distribution. — Canada to Georgia and westward to Mis- 

 souri. 



346 



