1941] 
Lepidoptera of the Dry Tortugas 
147 
THE LEPIDOPTERA OF THE DRY TORTUGAS 
By Wm. T. M. Forbes 
Cornell University, Ithaca, New York 
The Dry Tortugas occupy an unique space in the geo- 
graphy of the United States, being the only “Oceanic” 
Islands in the Gulf of Mexico. In a sense they would belong 
to the Florida Keys, being a continuation of the same forma- 
tion, but they lie so far beyond Key West (75 miles) that 
casual immigration would be limited to the stronger flyers ; 
moreover, they are so low that they most probably have 
been completely under water since the last glacial period. 
Presumably the whole fauna has come in by sporadic acci- 
dents during the last few thousand years. Naturally most of 
the species of the list are wide-spread, being found both on 
the Mainland and in Cuba, but the Litoprosopus may pos- 
sibly be endemic, — in any case it is more like the Bahaman L. 
hahamensis Hmps. than the Florida L. futilis. 
I owe the material to the kindness of Prof. H. H. Plough 
of Amherst College, who collected it in the summer of 1936. 
I have not noted any other records of Lepidoptera from 
the Islands. 
List 
Pieris monuste. Both phases of the female were taken, 
but not extreme. 
Nathalis iole. Garden Key. 
Theda columella. Apparently the commonest butterfly to 
judge by the number taken by sweeping. 
Plebeius filenus {hanno). This is the filenus of Bates’ 
“Butterflies of Cuba” and the hanno of most U. S. collectors. 
Holland figures something else (which I do not know) as 
filenus from Florida. In any case the Tortugas specimens 
are like those from the Antilles and the commoner form 
from Florida. 
P. ammon. A single specimen. 
