Aquatic insects play a pivotal role in connecting aquatic and terrestrial ecosystems through their metamorphosis from aquatic larvae to terrestrial adults. As metamorphosis itself is a physiologically stressful process, additional stressors in the aquatic ecosystem, such as contaminants, may result in metamorphic failure and disrupt this aquatic-terrestrial linkage. My thesis focuses on the effects that agricultural contaminants, such as herbicides, insecticides, and metals have on larval and adult aquatic insects, as well as the potential for the metal selenium to be transferred over metamorphosis. To understand the effects of agricultural activity on aquatic insects in the field, I studied how receipt of surface runoff or tile drainage outflow influenced larval and adult aquatic insects in wetlands, as well as how selenium concentrations varied in these wetlands and the tissues of the insects within them. Over two summers, I surveyed 18 wetlands in the Prairie Pothole Region of South Dakota that were receiving surface runoff, tile drainage outflow, or were surrounded by grassland. I collected larval and adult aquatic insects, and sampled for neonicotinoid insecticides and selenium from the water, and selenium from insect tissues. Selenium concentrations in the water, larval and adult insects, were the primary driver of differences among treatments, and selenium was retained over metamorphosis. To test the role of two common and co-occurring contaminants in affecting aquatic insect populations, I performed a six-week mesocosm experiment using environmentally relevant concentrations of atrazine, selenium, and a combination of the two. During this time period, I collected larval and adult aquatic insects, chlorophyll concentrations, water chemistry, and water quality. Adult aquatic insect populations were reduced at peak emergence by 35-45% in all treatments relative to the control, despite a lack of benthic response until several weeks later. These studies suggest that the effects of agricultural contaminants in the water may be partially externalized to the terrestrial ecosystem via reductions in quantity and quality of food for terrestrial consumers and highlight the important role that aquatic insects play in both environments.