Movement is one way herbivores respond to their host plant, yet the movement of relatively immobile insects has received little attention. We studied how the movement and density of apterous soybean aphids responds to a resistant soybean variety and different temperatures. In Chapter One, we examined aphid movement both within and between soybean plants that varied in their resistance to aphids. Aphids on resistant plants had a wider dispersal, apparently due to greater aphid movement. Consequently, aphids on resistant plants could move to neighboring susceptible plants, thereby increasing their density. In Chapter Two, we measured aphid density and dispersal on resistant and susceptible plants when insects and plants were exposed to two different temperatures. Here, movement behavior was affected by both plant resistance and temperature. Moreover, temperature and plant resistance interacted to influence aphid density. Our results indicate the important role that movement can play in an herbivore's response to plant resistance.