The SPBF uses woodland glades, mires, damp grassland and rush pasture, grassland with bracken or scrub and woodland edges with open glades, where violets Viola spp (particularly Common Dog Violet V. riviniana and Marsh Violet V. palustris) grow. In Yorkshire, marsh violet appears to support the butterfly on a majority of sites. In the west, Austwick Moss, Wharfe Woods (both VC64), Rise Hill (VC65) and other sites possess areas where the plant is abundant, but there are also patches of common dog violet occurring sparsely on adjacent drier land. In County Durham, egg-laying has been observed-on common dog violet adjacent to mires containing marsh violet and is considered to be an important site component (EIIis 2000).
However, the Yorkshire situation is unclear. Some North York Moors (VC62) sites are exclusively of common dog violet, which occurs in low densities on dry grassy bank edges, or amongst light bracken litter (e.g. the southern half of the Newton Dale population). Marsh violet sites are typically found on moorland mires, rush pasture or marshy grassland with a wet peaty surface and impeded drainage. The violets grow in discrete areas on the margins of the wettest mire habitats, usually within rush pasture and often on the sides of tussocks, which may be an important structural component in the ecology of both larvae and violets. On the North York Moors, this habitat is also found within coniferous forest, usually adjacent to a beck. In VC62 it is probable that in the past the butterfly was largely dependent on coppicing, but now exploits whatever suitable habitat remains. By contrast, in the west it seems to have been using the same mire habitats for two millennia (Whitaker 2002, 2003).
The most commonly used nectar-source is Marsh Thistle Cirsium palustre, although Ragged Robin Lychnis flos-cuculi and Cuckoo Flower Cardamine pratensis are occasionally visited and wild Raspberry Rubus idaeus is used at Raygate Slack. Although any small flower proud of the foliage can be picked out by the butterfly, it seems incapable of distinguishing those growing amongst leaves. To this end it has developed a technique, which involves crawling through the leaves and stalks, with proboscis unfurled and trailing beneath, in contact with the foliage, until a flower-head is encountered and the butterfly stops to feed (Sean Clough pers obs.). At Deepdale Meadow, the most abundant flower on one visit was Common Cat's-ear Hypochaeris radicata, which was used on 13 out of 16 visits by two nectaring females (Sean Clough pers obs.).