BODY TEMPERATURE REGULATION IN A LATE-SEASON DRAGONFLY, SYMPETRUM VICINUM (ODONATA: LIBELLULIDAE)

Abstract Body temperature regulation and behavioral responses to temperature variation in the field were investigated in Sympetrum vicinum, a common North American libellulid that is most abundant as a mature adult in autumn. Because of its late flight season, this species is faced regularly with cooler environmental temperatures than most dragonflies investigated heretofore. By virtue of postural adjustments and perch selection, individuals are able to maintain both thoracic and head temperatures within a relatively narrow range even at ambient temperature as low as 10 °C. Physiological adaptations, including relatively low minimum temperature for effective flight and relatively rapid digestive function at low temperature, also enhance their ability to cope with cool conditions. Copulation and tandem oviposition and mate guarding interfere with the ability to regulate body temperature, although oviposition was observed at air temperature as low as 14 °C.