Brimstones in the sun: thermoregulation
Whilst I was taking photographs of these beautiful Brimstone butterflies (Gonepteryx rhamni) nectaring on the little pink flower-pots of Bell heather (Erica cinerea), I noticed that they stopped when a cloud passed over. The day was relatively warm, but the site was on top of a small mountain, so when large clouds obscured the sun,…