Thermal flight budget of a woodland butterfly in woodland versus agricultural landscapes: An experimental assessment

We assessed the impact of vegetation structure and type of landscape on microclimatic conditions for flight activity, using the heliothermic butterfly Pararge aegeria as a model. Dummies (i.e., dead specimens with spread wings, on a hypodermic needle with a thermocouple) that initially were warmed up to similar thorax temperatures were able to cover larger distances, and they heated up faster, with higher ambient temperature and with lower wind speed. Convective cooling decreased with increasing degree of shelter, and with lower flight height. Simulated flight bouts bridged 140±23 m under unsheltered, 81±13 m under partly sheltered and 29±6 m under sheltered conditions. Ambient temperature and wind force were higher in highly fragmented, agricultural landscapes than in continuous woodland landscapes. Males, and not females, were furrier in agricultural landscapes. This sexual difference is interpreted in terms of differences in life history among the sexes.