The legacy of historical biogeography impacts many organisms and results in a wide range of character variation over a latitudinal gradient. The pitcher-plant mosquito Wyeomyia smithii is one such organism that demonstrates a wide range of phenotypic and genotypic variation over the entirety of its range from the Gulf Coast to Canada. A geographic cline established by the presence and recession of the Laurentide Ice Sheet is manifest in the narrow range of thermal tolerance exhibited by different populations and also in the differing propensity of bloodfeeding by these mosquitoes. These contemporary clines were analyzed by a variety of experimental methods ranging from year-long fitness assays, scanning electron microscopy, and RNA-sequencing to determine the patterns underlying the resulting evolutionary differences among established populations. This dissertation includes both unpublished and co-authored material.