The objective of this research is to determine the effect of local flow conditions on the distribution of a stream insect, emphasizing possible constraints on settlement from the water current. Although some studies have been done on this subject in marine environments, the consequences of hydrodynamic constraints on settlement have not been actively studied in freshwater systems. Transport by water currents in streams and rivers (drift) has been the object of intense work and debate, but very few studies have attempted to determine its significance to the individual organism. This study will be one of the first tests of the hypothesis of active drift as a foraging decision. This test will be aided by the development of a foraging model in which the organism has incomplete information of its environment. In itself the model will be an important addition to a field in which models and critical tests are still fragmentary. Black fly larval dispersal in a stream is largely analogous to the movements of ballooning spiders or lepidopteran larvae (including gypsy moth larvae), two groups that have been analyzed from a fluid mechanic point of view. What makes this system particularly interesting is the largely unidirectional nature of the movement. This relative simplicity will provide important insights that may be applied to the ecology of other organisms that are transported by air or water currents in some phase of their life cycle.
