Scott O’Neill is internationally recognized for his contributions to the field of insect symbiosis. His studies focused on Wolbachia have shown that intimate bacterial associations of invertebrates are ubiquitous and can generate major effects on the reproductive physiology, developmental biology and ecology of the insects they infect. His work has made major contributions to understanding how insect symbionts exert their effects and the consequences for infected hosts. An applied focus of his work has been the use of insect symbiont systems to establish innovative approaches to control insect transmitted diseases of humans such as dengue fever.