Activity in Heodes virgaureae (Lep., Lycaenidae) in relation to air temperature, solar radiation, and time of day.

The degree of activity of H. virgaureae in the field is largely dependent on air temperature, solar radiation, and wind velocity. Solar radiation increases body temperature above ambient. The butterfly orientates its back towards the sun and exposes the dorsal surface of the wings. At high temperatures they close the wings thereby minimizing the surface exposed to the sun. The optimal body temperature lies around 35°C as was indicated by laboratory experiments. In cloudy and cool to fairly warm conditions the butterfly is inactive. In sunshine the butterfly basks at low radiation intensities or low air temperatures while feeding (in males also flying) predominates at full sunshine or very high air temperatures (around 30°C). Males fly 5-10 times as much as females. A change from unfavourable to favourable weather is followed by an immediate increase in activity of the butterfly, which enables the butterfly to utilize short periods of sunshine.