Congratulations! - Master's Defensio


Stefanie Gruber

Messung der Thoraxtemperatur von Tagfaltern (Papilionoidea) im Freiland

Advisor: Harald Krenn

Master's Defensio

Monday, March 27th 2023, 11:00 am CET
online via Zoom


Butterflies’ temperature depends strongly on abiotic factors, but butterflies are also capable of active thermoregulation. The temperature of butterflies is relevant for understanding morphological structures, behaviour adaptations, metabolic processes, and the insect’s overall fitness. Knowing about butterflies’ capabilities of thermoregulation can provide insights into their adaptability to changing environmental conditions, including the impact of climate change. However, we currently lack actual temperature data for many butterfly species and how these temperatures relate to environmental temperature and body size. Until now, there was nonon-invasive method to measure animals in fieldwork at a standardized distance. This study analysed thoracic temperatures of butterflies in different elevations in Central Europe and their relationship to habitats, species, body size, and environmental temperature and assessed whether if larger butterflies are warmer. A simple, standardized non-invasive method for measuring thoracic temperatures of butterflies in the field is determined and tested by using aself-build tool out of an infrared nearfield thermometer.

The sample consists of 536 butterflies from four different families (Papilionidae, Pieridae,Lycaenidae, Nymphalidae) and 31 species. A deeper analysis was made of Pieris rapae because this species was found at all locations. Butterflies from lowland areas had higher temperatures (29.5 °C to 39.9 °C) compared to those from the Alpine area (14.5 °C to 33.2 °C), which applies as well to Pieris rapae. Forewing length, assumed as a measure for body size, showed no or low correlations with ambient temperature. In contrast, the thoracic temperature correlates with the body size moderately. The measured butterflies show a correlation between ambient temperature and thoracic temperature. However, the thoracic temperature of most butterflies was considerably higher than the ambient temperature, particularly in cold regions, while some individuals in very warm regions also had a lower body temperature than the surrounding. The average difference between the butterflies and ambient temperature was x between 4,6 °C and 8,6 °C.

A table of thoracic temperatures of various Central European butterflies is shown for the firsttime and compared to body size and ambient temperature. The applied new method is non-invasive and gives measurements of butterflies’ thoracic temperatures in the field that are important for understanding of activity and natural history of these insects.