The Duke of Burgundy is the sole representative of a subfamily known as the "metalmarks", since some of its cousins, particularly those found in south America, have a metallic appearance. A curious characteristic of this subfamily is that the female has 6 fully-functional legs, whereas the male has only 4 - the forelegs being greatly reduced. The Duke of Burgundy was once classified as a fritillary, given the similarity with those fritillary species found in the British Isles. This butterfly is found mainly in central southern England, although scattered colonies are found elsewhere such as in the north of England in Cumbria and Yorkshire. This species is not found in Wales, Scotland, Ireland, the Isle of Man or the Channel Islands. Although relatively-large colonies exist, most colonies only contain around a dozen individuals at the peak of the flight season.
There is one brood each year, with the adults emerging at the end of April in southern sites, peaking in the middle of May. A partial second brood may appear in some years, but this is the exception, rather than the rule, and only occurs in certain sites in the south of England.
The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.
This butterfly was, in the past, primarily known as a woodland butterfly, where it fed on Primroses growing in dappled sunlight, with a number of colonies in chalk and limestone grassland. However, the cessation of coppicing in woodlands has had a marked effect on this species, with many woodland colonies dying out as a result. Primrose is used as the larval foodplant in woodland, whereas Cowslip is used on grassland.
The sexes are similar in appearance, although the female tends to have more orange on the wings and rounder tips to the forewings. The male and female can also be distinguished by behaviour. The fast-flying males are extremely territorial and will sit on a favourite perch, darting out to inspect anything that might be a passing female. Once a virgin female is encountered, the two mate without any discernable courtship. This is usually in mid-morning just after the females have emerged. The flight of the female is not as rapid as the male and they are often seen when egg-laying as they move from plant to plant, landing on the edge of a leaf before curling their abdomen to lay on the underside of the leaf.
Adults only occasionally nectar, usually in warmer weather, with Wood Spurge, Buttercup, Hawthorn and Bugle being favourites. Both sexes roost in tall scrub or trees.
Eggs are normally laid singly, or in small batches of just 3 or 4 eggs, on the underside of the edge of a leaf of the foodplant. Nearby foliage may be used on occasion, especially when the foodplant is within dense vegetation. Large, lush, green-leaved plants are typically used, either among grasses or close to scrub. Snails are known to cause heavy losses of eggs, as they feed on primula leaves during the spring. Eggs hatch in 1 to 3 weeks, depending on the weather.
On hatching, the young larva eats its eggshell before moving to the base of the foodplant, feeding only at night. Larvae emerge at dusk, and can be found in torchlight, usually feeding on the upperside of the leaves. A tell-tale sign of a larva is a characteristic patchwork of holes made in the leaf surface, leaving the major veins intact. There are 3 moults in total and this stage lasts around 6 weeks.
The pupa is usually formed away from the foodplant in leaf litter, a grass tussock or other vegetation, secured by a silk girdle and the cremaster. It is believed that shrews are responsible for heavy losses during the pupal stage in which this species hibernates.
Long-term distribution and population trends show that this butterfly is in serious decline. It is therefore a priority species for conservation efforts. It is thought that this species is unable to survive intensive grazing of chalk and limestone grasslands and that this is, at least, one possible cause of the decline. It is also unable to tolerate areas where the foodplant becomes too shaded by surrounding shrubs and grasses. A delicate balance therefore exists that requires specific site management to cater for this delightful little butterfly.