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Insect emergence is a fundamental process in streams and rivers, because it represents a key life stage for aquatic insects and provides an important prey resource for terrestrial (e.g., birds, bats, and lizards) and aquatic consumers (e.g., fish). Studying insect emergence can lead to fundamental insights about the life history of insects, for example by identifying the specific times of year when emergence occurs. The number of insects emerging from a river is a function of larval population abundance in a river, so quantifying insect emergence might also be a useful proxy for standard benthic monitoring of insects; benthic monitoring in Grand Canyon is extremely challenging because of swift currents, deep water, and daily hydropeaking. In 2012 we started collaborating with commercial river guides (http://www.gcrg.org/) and Grand Canyon Youth (http://www.gcyouth.org/) to quantify insect emergence throughout the 240 mile long segment of the Colorado River in Marble and Grand Canyon. Each night in camp, guides put out a simple light trap to collect flying insects. After one hour, the light was turned off, the sample poured into a collection bottle, and some notes were recorded in a field book. After the conclusion of the river trip, guides dropped off samples and field notes at our office and we processed the samples in the laboratory.