Thermoregulation and Reproductive Activity in Tropical Dragonflies of the Genus Micrathyria

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Abstract
Observations of behavior, including time budgets, and measurements of body temperature are reported for four species of Micrathyria in the Panama Canal Zone. Larger species maintained an elevated body temperature by flying continuously at low ambient temperatures. All species probably thermoregulated behaviorally at high temperature. From data on body temperature during continuous fight and on heat exchange rates it is possible to estimate the energetic requirements for thermoregulation. In the smaller species, endothermy is prohibitively expensive. Temporal patterns of activity at breeding sites differed among species. The species that thermoregulated well extended their activity periods early and late in the day while the smaller, poorly thermoregulating species were restricted to midday activity. The extended activity periods of the large species apparently allowed them to reduce competition for perches and interference with mating and oviposition by other dragonflies.