Leptidea sinapis ssp juvernica Wood White
The weak, low flight of a white butterfly alerted us to the possibility of the presence of a Wood White which, in this part Ireland is a sub species found only on the Burren and in Galway. It has greener underwing than ssp sinapis.
In spite of its name it doesn't seem to feed on Sinapis (Charlock etc.) species but prefers plants such as Lotus corniculatus (Bird's-foot trefoil), Lotus pedunculatus (Greater Bird's-foot Trefoil).