9728444 Harrison While atmospheric composition has often been considered to be a constant, recent studies have demonstrated that atmospheric oxygen and carbon dioxide concentrations have varied substantially. In particular, geologic studies have suggested that the giant insects of the late Paleozoic coincided with atmospheric oxygen levels which exceed today's levels by at least 50%, leading to the suggestion that giant insects may have been made possible by this greater availability of oxygen. This leads logically to the proposition that the body size of today's insects are limited by atmospheric oxygen availability. This research will test predictions from this hypothesis. Specifically, the possibility that the safety margin for oxygen delivery decreases with increasing body size in insects will be tested. The experiments will be conducted using the American locust as models, because this insect: (1) reaches a large adult size, (2) varies widely in body size during development, and (3) has a well-studied respiratory physiology.
