We compared the distribution and diversity of select aquatic, semiaquatic, and terrestrial insects in the riparian zone of the American Fork River draining Mount Timpanogos, Utah. We focused on Brachycerous flies. We compared their distribution and diversity with that of the clearly aquatic orders Ephemeroptera, Plecoptera, and Trichoptera. Using malaise traps placed at six sites from the headwater spring to the valley floor, richness, abundance and distribution were measured. The mid-domain effect would predict that the greatest richness and abundance in species would be found at the mid-range elevation of the sampled gradient. Our data shows that richness peaked at mid-elevation, but contrary to this theory, the abundance was greatest at high elevation.   In addition one of the sites has revealed patterns not consistent with either the continuous gradient hypothesis or the mid-domain effect. We suspect this discontinuity to be the result of either anthropogenic perturbations or a disproportional influence of one tributary on the system. Continual sampling along the river and analysis of the retrieved data is occurring to better understand these differences.