Distinguished for his work on the ecology and taxonomy of Australian locusts and grasshoppers. He and his team have established the fundamental causes of locust outbreaks in eastern Australia, and thus provided the basic knowledge necessary for radical control. He has shown that phase changes occur in other Orthoptera also, and his critique of the phase theory has profoundly influenced the outlook of locust workers throughout the world. In addition to being a recognized authority on physical ecology, he has contributed to an understanding of colour variation and made significant advances in general taxonomy.