4 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
and C. dolosus and C. spinosus, species found in the central portion of 
South America. 
Culex tarsalis ranges from southwestern Canada through the western, 
central, and southern United States and into Mexico (Carpenter and 
LaCasse, 1955). This species demonstrates close affinity with C. 
abnormalis which extends from Colombia to central Brazil. 
All three of these species, indigenous to the Nearctic region, demon- 
strate considerable extensions into Mexico but none has been reported 
from Guatemala southward. Thus, it appears that all three species 
have close affinities with, and that their ancestors may have been 
part of, the Neotropical fauna. ‘The affinities of these three Nearctic 
species with the Neotropical fauna could be explained by Belkin’s 
(1962) hypothesis of the intercontinental origin of new types. This 
hypothesis suggests that the phylad originated on an island in the 
intercontinental area, dispersed to both hemispheres initially, and 
then continued evolving independently. 
The two principal intercontinental areas which Belkin (1962) con- 
sidered as primary centers of origin are the Indo-Pacific area between 
Eurasia and Australia, and the American Mediterranean between the 
North and South American continents (ibid., vol. 2, map on p. 18). 
It was his contention that these areas are the most likely places for 
the origin and evolution of new major types of mosquitoes. Both are 
characteristically unstable regions where major orogenic belts of 
adjacent continents meet, intersect, form arcs, or otherwise have 
complex relationships. Thus, in the course of island formation, great 
environmental stress would be imposed on the surviving populations 
and these would be greatly reduced and isolated. Under such con- 
ditions there would be an ideal opportunity for the quick fixation of 
new adaptive types of organisms. Examination of distributional 
patterns in the subgenus Culex indicates that the American Mediter- 
ranean is probably the primary center of origin. Forty-seven of the 
61 species considered in this study are found within the boundaries of 
this area as delimited by Belkin. 
Several endemic species are found on the Antillean and Bahamanian 
islands. Both Culex scimitar and C. sphinx have been reported only 
from the Bahamas and both show strong affinities in the male termi- 
nalia to C. nigripalpus, which is distributed throughout the southern 
Nearctic and American Mediterranean areas. C. duplicator is 
endemic to the island of Hispaniola and demonstrates affinity with 
C. saltanensis, a species with a distribution range from Venezuela to 
northern Argentina. C. finlayi has been reported only from Cuba. 
Although the male terminalia is somewhat unique, there seems to be 
some affinity with the more widely distributed C. chidesterr. C. 
bahamensis, a unique species demonstrating affinity with the subgenus 
