CATOSTOMIDjE THE SUCKERS 63 



buffaloes in collections is decidedly greater, according to our ex- 

 perience, than the corresponding average for the darters or the 

 sunfish, being represented, 'for suckers, by the general coefficient 

 of 2.45, for darters by 2.02, and for sunfish — that is, the Centrarchida 

 exclusive of the black bass — by 1.87. 



When full grown, the majority of the species are safe from any 

 enemies of their kind which the water contains, but their survival 

 to adult age is dependent on their fortune in escaping from a host 

 of predaceous and voracious fishes against which they have no 

 defense, and to whose depredations their haunts and habits freely 

 expose them. In the food of 1,221 Illinois fishes, representing 87 

 species, studied by the senior author during the dozen years pre- 

 ceding 1888, suckers and buffalo-fish were found most frequently in 

 the food of the pike, but occurred also in that of dogfish, bullheads, 

 sheepsheads, and sunfish. The sucker family would evidently 

 suffer much more severely, however, if it were not for the presence 

 in the waters they inhabit of the gizzard-shad, more abundant, ami 

 probably more accessible to pike and other predaceous fishes, than 

 are either suckers or young buffaloes. It is an interesting illustration 

 of the way in which companion species having little or nothing to 

 do with each other directly may nevertheless greatly influence 

 each others' welfare, that while 20 pike out of 37 had eaten 

 gizzard-shad, which made, in fact, nearly half the food of the entire 

 number, only 3 per cent, of their food came from the sucker family, 

 and this had been eaten only by three of the pike. 



Examining the other side of the food relation, we find that the 

 food of this family itself, as illustrated by a careful study of the 

 stomach contents of 109 specimens, belonging to five genera and 

 eleven species, consisted mainly of the smaller mollusks living in the 

 mud and larva; of aquatic insects, the two being about equal in 

 ratio and together making more than three fourths of the entire 

 food. Vegetation contributed less than 10 per cent, to the mass 

 examined, and no element of this class was especially prominent. 



The structures of alimentation vary noticeably in definite 

 directions as one passes along the series from the most cylindrical 

 suckers to the thin and deep-bodied buffalo and carp. In the 

 former the pharyngeal bones are heavy, and the lower teeth are 

 thick and strong, usually with a well-developed grinding surface, 

 while the gill-rakers are short, thick, and few, and the intestine is 

 comparatively short and large. As the body deepens, the pharyn- 

 geal bones become longer, the pharyngeal teeth smaller and more 

 numerous, with diminished grinding surface; the gill-rakers 



