MEd student (Adv. Harald Krenn)
Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna

Abstract 

Butterflies are ectothermic metazoa. Therefore, their body temperature highly depends on environmental conditions. Nevertheless, the body temperature can be regulated within a certain range by behavior like basking in the sun. This behavioral thermoregulation is an important condition enabling butterflies to fly in cold conditions. Recent studies indicated internal processes that may stabilize the thorax temperature that seems to be relevant for flight. However, a simple question remains to be answered: What is the thorax temperature of an active butterfly in natural habitat of temperate zones? In this master thesis, the actual thorax temperature and of 536 butterflies from 31 species was measured at three locations in Austria along different high altitudes, under various air temperature and sun exposures. For this purpose, a contact-free near-field measurement technology with an infrared thermometer was used for measuring the cuticle of the thorax with pinpoint accuracy. Differences of the thorax temperatures ranged between +14,5 and +39,5 degrees in the studied butterfly species. The temperature was higher than the ambient temperature with an average discrepancy of +8.39° C (+/- 3,53). The data indicates that large butterflies are warmer than smaller species. The results suggest that mean body temperature of butterflies in higher altitudes is smaller compared to lower altitudes. The method used in this study proofed to be well applicable for field studies and can be used for further studies on butterfly temperature measurements to understand butterfly activity under natural conditions.