ANNOTATED LIST OF FISHES 



125 



elongated and bear bony hooks at the tips. It then forms an organ used in conveying the sperms 

 from the male to the female. 



The species of this genus are highly useful for the reduction of mosquito breeding. A large 

 degree of natural control is provided by these fish throughout the South, cast of the Rocky Moun- 

 tains, where their distribution is quite general. In a number of the Southern States efforts have 

 been made to distribute Gambusia to waters it had not reached through natural channels. 

 Gambusia has been introduced in several States and many foreign countries to aid in abating the 

 mosquito nuisance. In some localities it has not survived because the winters were too cold; 

 in others it met enemies it could not combat. Several importations, as in Italy, Spain, and the 

 Hawaiian Islands, have proved very beneficial. For an account of a rather exhaustive study of 

 the effectiveness of Gambusia as an eradicator of mosquito larvse, the reader is referred to Public 

 Health Bulletin No. 153, United States Public Health Service (1925, Washington). Gambusia 

 holbrooki was used in the studies reported upon in this bulletin. Somewhat similar studies were 

 carried on later with Gambusia patruelis, which gave similar results. It may be stated that in 

 general the degree of mosquito control provided depends partly upon the number of fish present 

 but to a greater extent upon the amount of protection against fish which the mosquito larva? 

 receive from the presence of plants and flotage. 



26. Aphredoderus sayanus (Gilliams) 



Pirate perch 



Scolopsis sayanus Gilliams, Jour., Acad. Nat. Sci., Phila., IV, 1824, p. 81. 



This fish probably is not abundant locally, as only nine specimens, ranging in length from 48 

 to 87 millimeters (2 to 3% inches), were taken. The pirate perch is of much interest to the 

 naturalist who has not yet been successful in explaining satisfactorily the unusual phenomenon 

 of the change in position of the vent that takes place with age. For the vent is "normally" 

 placed in the young; that is, it is posterior to the ventral fins. It gradually moves forward, how- 

 ever, as the fish grows, and finally occupies a place on the isthmus between the gill covers. Forbes 

 and Richardson (1908, p. 231), in discussing this subject, state that a comparison of food of speci- 

 mens of various ages gave no hint for the reason of this extraordinary step in development. 



The rather unusual development of the pelvic girdle, which arches into the center of the ab- 

 dominal cavity, thereby reducing the space somewhat, may have some correlation with the 

 anterior position of the vent in the adult. In adult perch the pelvic arch is traversed by the small 

 intestine, which enters the arch posteriorly and proceeds anteriorly to the jugular vent. The 

 small intestine is comparatively short, averaging only about 25 per cent of the total length of the 

 fish, and by traversing the girdle in its anterior progress along the floor of the abdominal cavity 

 it occupies a space that could not be used more economically by another organ. An examination 

 of nine stomachs showed that immature insects, principally midge larvse, had been taken by the 

 pirate perch, with virtually no other food in evidence. Forbes and Richardson (1908, p. 230), 

 in examining 19 stomachs, also found most of the food to consist of insects and insect larva?, and 

 only two of the specimens had eaten fish. 



Two females taken at Greenwood on September 30, 1925, were approaching the spawning 

 period; the larger of these, measuring 87 millimeters in total length, contained approximately 

 1,100 eggs. Forbes and Richardson (1908, p. 231) found spawning fish at Meredosia, 111., in 

 May. This appears to suggest a long spawning period. The nine specimens at hand were taken 

 from borrow pits on the Itta Bena Road and the Grenada Road. 



27. Boleosoma camurum Forbes 



Boleosoma camurum Forbes, Bull., 111. Lab. Nat. Hist., II, 1878, p. 40. 



This small darter is represented by 14 specimens, ranging in length from 32 to 43 millimeters 

 (1'4 to 1% inches). The species is characterized by the incomplete lateral line, which extends 

 only under the spinous dorsal, and by the distantly placed dorsal fins, the tips of the spines of 

 the first dorsal scarcely reaching the origin of the second dorsal when deflexed. The cheeks, opercles, 

 and chest are all fully scaled in the specimens at hand. 



