Where to see
Habitat: Large areas of deciduous or mixed woodland, though it may use smaller areas if its foodplant is present in quantity. It is a mobile butterfly, so it may be able to use smaller areas grouped fairly close together.
Caterpillar foodplants: Mainly Goat Willow (Salix caprea) but also Grey Willow (Salix cinerea) or occasionally Crack-willow (Salix fragilis).
Best places: All sightings in woods have been in the Cranborne Chase area. They seem most likely to be breeding in Garston Wood, which is ancient woodland managed as a RSPB reserve, since both a female and an egg have been reported here. Males have also been reported in Chase Woods.
When to see
Single brood. Mainly July, but maybe into June or August.
Sightings by month (last 5 years)*:
Sightings this year*:
The Purple Emperor is a large butterfly, which spends most of its time up in the trees, feeding on sap and honeydew (which is sap partly digested by aphids). The males (only) will sometimes come down to feed on salts contained in dung, rotting flesh or puddles; they will also land on humans, as can be seen in the photos below, presumably for the same reason. The female is rarely seen.
The upperside of the male Purple Emperor will look different depending on the light: from dusky brown/black through to an iridescent purple. The female does not have this purple sheen, but has bolder markings and is slightly larger. Both sexes have an orange eyespot at the base of the hind wing. The undersides of both male and female have the same white markings as the uppersides, but the background colour is a mix of brown, pink and silver.
The only butterfly with which the Purple Emperor can be confused is the White Admiral, but the Purple Emperor is quite a bit bigger and has more pointed wings. Close up, the White Admiral lacks the orange markings on the upperside of the Purple Emperor and the undersides are very different.
*Note: The charts shown on this page are drawn only from casual sightings submitted to this website. Records from this website will be added to a lot more data collected throughout the year and used to compile the five-yearly Butterfly Atlases for Dorset and the UK.