Temperature, incubation rates and origins of dragonflies

The slope value (b) of the power equation (lnD = lna + blnT) relating degree-days required for development (D) to temperature (T) in insects is a composite measure of temperature adaptation that is of higher negative value in warm-adapted species than in cold-adapted species. Temperate-zone dragonflies for which data are available have high negative slope values in the egg stage. This contrasts with temperate-zone stoneflies, which probably evolved in cold-temperate regions and are uniformly cold-adapted, and with temperate-zone mosquitoes, whose slope values decrease as species range further north. Temperate-zone Odonata appear, therefore, to have retained the characteristics of their tropical ancestors.