42 ILLINOIS BIOLOGICAL MONOGRAPHS [42 



50. Schilbeod.es gyrinus (Mitchell). Tadpole Cat. 



This little stonecat is, like the members of the entire group, an inhabit- 

 ant of clear rapid water, where it is associated with Noturus flavus and 

 various darters. I have taken it only in the Oconomowoc river at Stone- 

 bank, where it lives in the riffles under stones, cans, logs or any other avail- 

 able covering. The food is entirely animal matter, similar in composition 

 to that of the preceding species. That breeding occurs late in May is 

 indicated by the fact that while I have taken many gravid females before 

 May 15, I have never seen one after May 25. 



51. Schilbeodes exilis (Nelson). Slender Stonecat. 



Also from the Oconomowoc river at Stonebank, and twice I have taken 

 the species in the Mukwonago river. The rarest of the genus within our 

 limits. Food and habits apparently very similar to the preceding species. 



52. Schilbeodes miurus (Jordan). Brindled Stonecat. 



Strangely enough, this species, while inhabiting very similar waters, 

 has never been taken by me in association with either of the preceding. 

 My specimens have come almost entirely from the Menomonee river, and 

 for a long time I thought the species was limited to the Lake Michigan 

 drainage area. But in June, 1925, I took two specimens from the very 

 headwaters of the Fox river near Lannan. The fish inhabit running water 

 but seem to avoid the fast current preferred by the two preceding stone- 

 cats. They likewise live largely under stones, logs or other protecting 

 objects but seek water of a somewhat greater depth, two feet as against a 

 foot or often less for the other species. They also show a somewhat greater 

 tolerance for muddy water but are never found in water that approaches 

 opaqueness. The food is, again, entirely animal, largely larvae of Chirono- 

 mus, Hydropsyche, Aconeura and various species of mayfly, and small 

 dragon-fly nymphs. The stonecats are not separated by natives and are 

 all grouped together as "young bullheads." 



Order HAPLOMI 

 Family umbridae 



53. Umbra limi (Kirtland). Mud Minnow. 



An abundant inhabitant of the innumerable small, muddy vegetation- 

 choked ponds scattered throughout the region, and also in streams of a 

 similar character. Among the latter I have taken the species from the 

 headwaters of the Fox river in association with Esox americanus, Schil- 

 beodes miurus, Catastomus commersonii and the crayfish Cambarus propin- 

 quus. In this stream it provides one of the chief foods of the grass pickerel. 

 In the ponds it is most frequently associated with Ameiurus melas. No 

 water seems too foul or too stagnant for these fish and no ordinary amount 

 of drying up of ponds during a hot dry summer seems to exterminate them. 

 They seek refuge in the soft muck of the bottoms, often completely burying 



