The life history of an organism may be influenced by both features of the physical habitat and phylogenetic history.  Life history characters such as life cycle and body size may be variable as a result of differences in thermal regimes, rainfall and flood events, and even substrate mobility.  Alternatively, some life history features may lack variability, features that are fixed as a result of evolutionary history.  We studied the relationship between environmental features (latitude, altitude, temperature, and discharge) and phylogenetic history on the body size of adult Oligophlebodes (Trichoptera: Uenoidae) caddisflies.  Oligophlebodes is a small genus of stone-cased caddisfly with seven recognized species limited in distribution to high elevation streams (>1,200 meters a.s.l.) in western North America.  We measured body size, a parameter that may be representative other life history features such as fecundity and voltinism, of individuals from North American natural history collections.  To examine the effect of physical habitat, we determined altitude and latitude by georeferencing collection localities and acquired additional habitat parameters such as discharge and stream flow from the USGS National Water Information System.  To examine the effect of phylogenetic history, we constructed a morphological phylogeny of Oligophlebodes and examined trends using comparative phylogenetic methods.