Bumblebees are perhaps the most important of all pollinators of plants in the Arctic. Their ability to perform at low air temperature is based on their remarkable ability to produce heat by shivering and to keep warm in order to remain active. But shivering only affects the thoracic muscles that drive the wings. The abdomen, which contains no heat-producing tissues, remains cold unless heat is shunted to that area from the exercising flight muscles. In order to reproduce and live in the Arctic, the bees must squeeze their entire life cycle into a single, short summer. For them, time is temperature; to accelerate egg production and development rates they must also keep the eggs warm. The investigators plan to examine the hypothesis that Arctic bumblebee queens "incubate" their eggs not only after they are laid, but also while they are still developing in the abdomen. The energy cost of this heat production is likely very high. But it must be met because of the time constraint. This investigation will help determine the importance of temperature regulation in the evolution of the unique life history of the bumblebee and will further elucidate one of the many patterns of adaptation employed by animals in the harsh, yet fragile Arctic environment.
