SIMULTANEOUS CONTROL OF HEAD AND THORACIC TEMPERATURE BY THE GREEN DARNER DRAGONFLY ANAX JUNIUS (ODONATA, AESHNIDAE)

摘要

Anax junius is a large dragonfly that regulates thoracic temperature (T-th) during flight. This species, like several other intermittently endothermic insects, achieves control of T-th at least in part by increasing circulation of hemolymph to the abdomen at high air temperature (T-a), thus facilitating heat loss from the thorax. In this paper, I demonstrate that heat transfer to the head is also under active control, very probably owing to temperature-sensitive alteration of hemolymph circulation. As a result, head temperature (T-h) is strikingly elevated above T-a during endothermic warm-up and flight, Furthermore, during unrestrained flight in the field, T-h is regulated actively by increasing hemolymph circulation from the warm thorax at low T-a. Concurrent measurements of abdominal temperature (T-ab) confirm that the abdomen is used as a 'thermal window' at T-a>30 degrees C but apparently not at lower T-a; thus, some additional mechanism(s) must exist for regulation of T-th at low T-a. [References: 30]