224 FISHES OF ILLINOIS 



Genus PYGOSTEUS Brevoort 



NINE-SPINED STICKLEBACKS 



Dorsal spine 9 to 11, divergent from right to left at various angles; tail 

 broader than deep, with a lateral bony keel; pubic bones weak and feebly 

 united, forming an elongate plate with a median longitudinal groove, on each 

 side of w r hich is a raised edge*; characters otherwise as in Eucalia. Species 

 two, in the waters of northern regions, one of them native in China; a single 

 species, cosmopolitan in distribution, found in the w r aters of Illinois. 



PYGOSTEUS PUNGITIUS (Linn.eus) 



NINE-SPINED STICKLEBACK 



Linnaeus, 1758, Syst. Nat., Ed. X, 296 (Gasterosteus). 



G., I, 6 (Gasterosteus); J. & G., 393 (Gasterosteus); M. V., 97; J. & E., I, 745; N., 

 42 (nebulosus); J., 51 (occidentalis var. nebulosus); F. F., I. 6, 69. 



Length 3 inches; body quite slender, considerably compressed, the 

 caudal peduncle very long, slender and tapering, broader than deep, and 

 with lateral bony keel; depth 5.1 to 5.6; greatest width about % of greatest 

 depth; depth of caudal peduncle 4.3 to 6.2 in its length. "Color olivaceous 

 above, profusely punctulate, irregularly barred with darker; silvery below" 

 (J. & E.). Head 3.3 to 3 7; width 2.4 to 3; interorbital space 4.5 to 5.1 in 

 head; eye 3; nose 3.3 to 3.8; mouth somew'hat less oblique than in the last 

 species, the maxillary nearly to orbit, 3.3 to 4.4 in head. Dorsal IX (or X), 

 9 or 10, the spines promiscuously divergent to right and left at various angles; 

 caudal scarcely lunate; anal rather low, the spine nearly as long as anterior 

 rays; ventrals with a long finely serrated spine, which is less than 3 in head; 

 pectorals 1.7 to 1.9 in head; post-pectoral plate well developed; thoracic 

 processes prominent, forming a U-shaped figure; pubic bones thin and feebly 

 united, lanceolate, with a median groove between two raised edges. Skin 

 naked except for small bony plates along bases of dorsal and anal and on 

 caudal keel. 



This little species has been taken by us but once, and then 

 from the lower Calumet River and from Lake Michigan near the 

 mouth of that stream. It inhabits both fresh and brackish 

 water, and is found throughout northern Europe, and in North 

 America as far southward as the Great Lake region. It is thus 

 a strictly northern species. 



Our only hint of its food was given us by the examination of 

 two specimens which had fed wholly on the larva? of gnats 

 (Chironomus and Simulium) and on various Entomostraca. 



* Not verified for P. sinensis of China. 



