©Si Barber. Moral rights asserted   Small Cabbage White butter fly (Pieris rapae) at Wicken Fen in Ely,Cambridgeshire. Wicken Fen is one of only four wild fens which still survive in the enormous Great Fen Basin area of East Anglia: 99.9% of the former fens have now been replaced by arable cultivation. It is home to a wide range of insect and wildlife species.