French to English Science Environment & Ecology butterflies

All I have managed to find out, so far, is that there seem to be 89 species of blue butterfly (in the UK?). This may be the 'common blue', but I am having difficulty in verifying this.
It comes in a set of clues for a game about wild flowers, birds and amphibians/reptiles. The description is as follows:
'Ce papillon est incontournable des pelouses des coteaux, sur lesquels il retrouve sa plante hote : une petite fleur jaune'