124 



BULLETIN OF THE BUREAU OF FISHERIES 



The species is named for W. H. W. Komp, of the United States Public Health Service, who 

 was engaged at Greenwood, Miss., in research pertaining to malaria when the present collections 

 were made. Mr. Komp rendered much valuable aid in the conduct of the work and the authors 

 take pleasure in naming this fish for him. 



This small fish was taken only in a borrow pit near the Itta Bena Road, where it was very plenti- 

 ful, frequenting a growth of primrose willow, Jussisea diffusa, along the shallow margins, with Gam- 

 busia, whose dwelling and feeding habits it appears to simulate. It is a more active fish than Gam- 

 busia, however, and better suited to survive where game fish are present in numbers, which was the 

 condition in this pond. A determination of its food was not made from stomach examinations; when 

 confined in an aquarium, mosquito larvae were taken readily shortly after the fish was captured. 

 The tract is short and thick-walled, approximating three-fourths of the length of the fish. A gavid 

 female, 63 millimeters long, was taken in June, its ovary containing 150 eggs. 



25. Gambusia patruelis (Baird and Girard) 

 Top minnow 



Heterandria patruelis Baird and Girard, Proc, Acad. Nat. Sci., Phila., VI, 1854, p. 390. 



We follow Hubbs (1926a, p. 38) in using the specific name patruelis, replacing the name affinis, 

 long used for this species. Mr. Hubbs produced evidence indicating that affinis apparently belongs 

 to another species, which seems to be of limited distribution, being known, to date, only from the 

 San Antonio-Guadalupe River system of Texas; whereas the present species ranges from southern 

 Indiana and Illinois southward to the Gulf coast. Due to its wide distribution, abundance, and 

 top-feeding habits, this minnow is a factor of importance in the control of mosquito breeding and is 

 widely employed in the South for this purpose. It is extremely prolific and swarms in virtually all 

 permanent waters where conditions favor mosquito production. 



Its diet is varied, and besides insects and other animals of suitable size it has been found to utilize 

 vegetation and even the young of its own species. There is only a slight stomachic dilation, and the 

 relative length of the intestinal tract apparently varies with the sex. In six adult male specimens, 

 28 to 31 millimeters long, it averaged 42 per cent of the total length of the fish; whereas in six females, 

 35 to 39 millimeters long, it averaged 57 per cent of the total length. 



The eggs of Gambusia develop within the female, and the young are brought forth at a relatively 

 well-developed, active stage and having an average length of 8 millimeters. The breeding season 

 commences in the early spring and continues through August and, to a limited extent, into Septem- 

 ber. The size of the brood in general varies with that of the female parent. For example, a 29-mil- 

 limeter fish produced 5 young, whereas a 50-millimeter fish produced 77 young. Broods ranging 

 upward of 200 fish have been reported for the related species G. holbrooki. 



It has been shown by Barney and Anson (1921, p. 58) and Hildebrand (1927, p. 392) that a great 

 seasonal difference takes place in the sex ratio of adult Gambusia; that is, the males are proportion- 

 ately much fewer in midsummer than during the rest of the year. The difference, according to rather 

 extensive statistics recently produced by Hildebrand, vary from 1 male to 2.54 females in June to 1 

 male to 11.3 females in August. Hildebrand also produced extensive evidence in corroboration of 

 Geiser's (1924, p. 198) contention that a 1 to 1 sex ratio exists in young Gambusia. The question 

 then arises, what becomes of the males afterwards? A definite answer can not be given, but Geiser 

 (1924, p. 201) and Hildebrand (1927, p. 400) have produced evidence showing that the males are less 

 resistant than females to adverse condition, and it seems probable that the males constitute the 

 weaker sex. It appears to be of interest to mention, in this connection, that among a lot of 184 

 adult Gambusia taken from a slough at Browning on August 6, which were heavily infested with a 

 parasite forming conspicuous external cysts, the ratio was 1 male to 25 females. Possibly the 

 scarcity of males was due to their low resistance to the parasite. Although the males were few in 

 this slough, the minnows were numerous, notwithstanding the fact that it was a favorite place for 

 collecting Gambusia for bait. 



Gambusia were present in all local waters, with one exception, this being a borrow pit at Money, 

 where the crappie is abundant and protection in the form of marginal vegetation is almost absent. 

 The most favorable habitat was in a section of a brook that passes through a hog yard situated near 

 the city. Several hundred Gambusia were collected. The largest males were 33 millimeters (1J*£ 

 inches) long, and the largest females were 50 millimeters (2 inches) in length. The male is not dis- 

 tinguishable externally from the female until it attains a length of about 20 millimeters, at which 

 size the anal fin usually has assumed its characteristic form — that is, the anterior rays have become 



