Data from: Warmest spring on record in the UK provides insights into how a specialist spring-flying butterfly may respond to future climate change

The Duke of Burgundy (Hamearis lucina) is a vulnerable species of
conservation interest in the UK. Previous research has suggested that the
butterfly is sensitive and vulnerable to temperature increases, with a
strikingly limited ability to maintain a stable thoracic temperature
across a range of air temperatures compared to other butterfly species.
However, these calculations were limited by the narrow range of air
temperatures in which thoracic temperatures were measured, as air
temperatures above 20 °C are rare during the spring flight period of this
butterfly in the UK. During the warmest spring in the UK since records
began, we measured the body temperatures of six adult Duke of Burgundy
butterflies at Totternhoe Nature Reserve, Bedfordshire, at air
temperatures over 20 °C. Together with existing data, we used this
information to recalculate a buffering ability for the Duke of Burgundy.
We found that adult Duke of Burgundy shows a greatly improved ability to
buffer its body temperature when including additional data points from air
temperatures of 24.2-25.9 °C. Our findings indicate that the Duke of
Burgundy is better at altering its thoracic temperature than previously
thought, and hence may be less sensitive to increasing temperatures than
predicted. However, our data also suggest that the Duke of Burgundy has
narrow temperature requirements, which may contribute to vulnerability to
climate change. Our research demonstrates the value of opportunistically
gathering data in unusually hot weather and highlights the importance of
research efforts exploring the thermal and habitat requirements of
specialist butterflies.