1969] 
Burns and Kendall — Pyrgus 
43 
surface of the uncus in oileus (giving the effect of a “double scoop”) 
as opposed to the simple convex dorsal uncus surface in philetas , the 
more heavily dentate gnathos in philetas , and the more delicate apex 
of the aedeagus in philetas ; and, in females (figs. 3 and 4), to the 
highly distinctive sclerotization around the ostium bursae in the two 
species, the much larger wrinkled membranous sac ventral to the 
ostium bursae in oileus , and the very different proportions and con- 
figurations of the major sclerotization (sterigma.) between the ostium 
bursae and the ovipositor lobes in the two species. 
Virtual allopatry in the United States 
Despite extensive Mexican sympatry, it appears that, in the south- 
ern United States, where these related but distinct species reach their 
northern distributional limits, they are practically allopatric. They 
seem, moreover, to be ecologically segregated — P. oileus to moister 
and typically (though not exclusively) coastal-plain environments, 
and P. philetas to drier interior ones. 
The United States distribution of these species can be summarized 
at two levels as follows. In broad view, P. oileus ranges from Florida 
to central Texas, and P. philetas from central Texas to Arizona. On 
state by state inspection, P. oileus is clearly widespread and common 
in the Florida Keys and in peninsular Florida, extending as far north, 
at least, as Gainesville, Alachua County; and it is known also from 
Escambia County bordering the Gulf of Mexico in the western tip 
of Florida adjacent to Alabama (Kimball 1965: 52). Although it 
is not yet reported from either Alabama or Louisiana, Mather and 
Mather (1958: 93) recorded the capture of 1 male in 1957 at Bay 
St. Louis, Hancock County, Mississippi; and, in i960, with the aid 
of M. and E. Roshore, they collected a total of 6 males and 4 females 
from four localities in Jackson County, Mississippi. Both Hancock 
and Jackson counties border the Gulf of Mexico. (All 11 Missis- 
sippi specimens have been examined by Burns.) Pyrgus oileus occurs 
primarily in southern sections of east and central Texas; but a single 
female has been reported from as far north as North Little Rock, 
Arkansas (Freeman 1945: 61). Pyrgus philetas ranges from central, 
southcentral, and west Texas to southern New Mexico and southern 
and middle Arizona. Not known from California, it conceivably 
could be found in the extreme southeastern part of that state. 
Narrow sympatry in Texas 
Since Texas is the only one of the United States in which P. oileus 
and P. philetas meet, we have, for several years, in the course of other 
