SKINNER, E.C.**; BENNETT, V.A.; Clarion University of Pennsylvania; Clarion University of Pennsylvania: Comparing seasonal changes in metabolism and cold-hardiness of winter- and summer-emerging stoneflies

Low temperatures of winter place stress on many organisms. Insects have developed a variety of adaptations that allow them to avoid harsh conditions. Some insects have periods of dormancy during the winter. Some can change their body chemistry to allow bodily fluids to cool far below 0°C without freezing, a process known as supercooling. Insects such as stoneflies and mayflies seek refuge as juveniles in relatively warmer and more thermally stable aquatic environments. The majority of species remain in streams through winter and emerge to mate as adults into a terrestrial environment during summer. However, some stonefly species (families Capniidae and Taenopterygidae) actually emerge from streams into the terrestrial environment in late winter (January-March), often with snow still on the ground. This study aims to compare the seasonal patterns of metabolism, activity, and cold tolerance between summer emerging and winter emerging stoneflies. We are collecting insects each season from streams in northwest Pennsylvania. Stream and air temperatures are being monitored throughout the year using data loggers placed at insect collection sites. Metabolic rates will be measured using a dissolved oxygen meter to obtain the rate of oxygen consumption. Summer emerging species (family Perlidae) may enter a dormant stage and reduce metabolism during the winter, but winter emerging species are expected to remain active with higher metabolic rates in preparation for emergence. Supercooling points are also measured in nymphs and emerging adults. We expect greater cold-tolerance in winter emerging stoneflies, particularly in the adult stage.