The American Midland Naturalist 
PUBLISHED BI-MONTHLY BY THE UNIVERSITY 
OF NOTRE DAME, NOTRE DAME, INDIANA 
VOL. VIII. MARCH anp MAY, 1923. NOS. 8-9 
Notes Relative to the Species of Gambusia in the United States. 
S. W. GEISER, 
WASHINGTON UNIVERSITY, SAINT LOUIS. 
(From the Zoological Laboratory of the Johns Hopkins 
Un iversity.) % 
REGAN (13) in his revisional paper on the viviparous 
Poeciliidae or top-minnows of the wor!d has ascribed to the 
territorial limits of the United States three species of the 
genus Gambusia; holbrooki, patruelis, and affinis. He main- 
tains that Gambusia holbrooki (Grd.) Guenth. is distributed 
from “Virginia to Alabama;” G. patruelis (B. & G.) Grd. 
from ‘Florida to Texas;” and G. affinis (B. & G.) Grd. 
from “Florida to Tampico; Mississippi.” Owing to the 
rarity of males in field-collections of Poeciliide, he had 
no males of some of the different “species” for comparison; 
and hence the descriptions which he gives of the different 
“species” do not appear to really satisfactorily differentiate 
them from other “species.” Color-markings, for example, 
may vary widely; the ground-color, also may differ markedly 
in the different habitats. The characters which he used in 
differentiating species, in fine, vary so greatly that it is 
impossible to clearly discriminate between his species. 
As a result of this, and in view of the remarkable diversity 
in the form and the color of Gambusia contemporary workers 
* My heartiest thanks are due to Professor S. O. Mast and Mr. S. F. 
HILDEBRAND. The work was done under the direction of Professor 
Mast, and to him the writer is indebted for valuable suggestions and 
help. Mr. HILDEBRAND supplied much valuable material which otherwise 
was inaccessible, gave notes on distribution, and contributed otherwise. 
I am indebted to both Professor Mast and Mr. HILDEBRAND for criti- 
cising the manuscript. 
