NOTES ON THE LIFE HISTORY OF THE MINNOWS GAMBUSIA 

 AFFINIS AND CYPRINODON VARIEGATUS. 



By Samuel F. Hildebrand, 

 Director, United States Fisheries Biological Station, Beaufort, N. C. 



INTRODUCTION. 



The observations and experiments upon which the present paper 

 is based were made in the Beaufort, N. C, region, partly in the 

 laboratory and partly in the field, from April, 1914, to October, 1915. 

 Only living fishes are considered and the experiments in aquaria 

 have probably afforded the most interesting data. While some of 

 the observations here recorded are in general harmony with the 

 published statements of previous investigators, yet they are fomid 

 to present such essential points of difference as to make it advisable 

 to include them in the present paper. The fact that these and other 

 minnows are now so highly esteemed as Agents for the destruction of 

 mosquito larvae in ponds and reservoirs lends a timely interest to the 

 publication of any data relating to the habits and propagation of the 

 species. 



GAMBUSIA AFFINIS (Baird and Girard). THE TOP MINNOW. 



NATURAL HISTORY. 



This top mimiow is known on the Atlantic coast from Delaware to 

 Mexico and in the Mississippi Valley from lUmois to Louisiana. It 

 inhabits both fresh and brackish water, while an occasional straggler 

 is taken in strictly salt water. Locally it is the only viviparous 

 teleost known. It may be found in nearly all shallow streams or 

 ponds of brackish or fresh water, and it is particularly abundant 

 m certain very shallow and muddy arms of the Mullet Pond on 

 Shackleford Bank. Nowhere, however, was it found to grow so large 

 as it does in a small fresh-water pond on Gallants Point. Females 

 taken from this very shallow and extremely dirty pond, visited daily 

 by both cattle and hogs, are from 60 to 65 mm. in length, while the 

 largest specimens obtained elsewhere do not exceed 45 mm. The 

 males, as is well known, are much smaller than the females. The 

 largest male observed in this vicinity was 33 mm. in length, which is 

 probably 6 mm. above the average. 



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