Drought Resistance in Subalpine Nymphs of Somatochlora semicircularis Selys (Odonata: Corduliidae)

Abstract

Somatochlora semicircularis inhabits subalpine pools and water meadows which frequently or regularly dry up in late August and early September. Since the nymphs require 4 years to mature, they must have the ability to survive these periods of drought. Somatochlora nymphs were found under rocks, moss mat, logs and deep in the bases of sedge clumps in Irwin Pond, Colorado. after it had dried up. In the laboratory, nymphs of Somatochlora die after losing the same relative amount of body water content under experimental desiccating conditions as do nymphs of Aeschna interrupta interna and Libellula quadrimaculata. However, it takes the nymphs of Somatochlora almost twice as long to reach this noint. Low rate of transpiration in the nymph and early formation of the snow pack over the dry subalpine pond are believed to contribu.te to the survival of this dragonfly.