The 'Duke' used to be known as the Duke of Burgundy Fritillary but although its wing patterns resemble those of the fritillaries it is not a member of the same family, it is the only British member of the metalmarks (Riodininae). Like so many of our butterfly species it has suffered greatly from loss of its preferred habitat and is now quite scarce. It likes west facing chalk or limestone grassland habitat and whilst there are still suitable sites like this in Dorset there seems to be only one publicly available location where the Duke of Burgundy can be seen. The larvae food plants are primrose and cowslip and so it also used to thrive in coppiced woodland but the decline of active coppicing has seen many colonies die out.
The Duke of Burgundy flies in a single generation from early May until mid June but, with just sixteen records in the Nature of Dorset database for 2017 and 2018, we do not have much to go on. The reports we do have show emergence in week 18 in Mid May and then there are reports each week until week 21 in mid June, just a four week window to see them. Of the sixteen records we have fourteen were from 2017 and just two from 2018, they were difficult to find last year which is a worry; I wonder what 2019 will bring?
Here in Dorset all of the reports come from Giant Hill at Cerne Abbas and this is west facing chalk grassland. There are records from survey data that has been found suggesting three other sites but I believe that the Duke of Burgundy may have gone from those now. Keeping the Giant Hill population is vital to the butterfly's future here in Dorset.