Silver-washed Fritillary Argynnis paphia, male, Wiltshire, England

Introduction

The Silver-washed Fritillary is one of Europe's largest and most magnificent butterflies. The male, illustrated above is easily distinguished from the female by the 4 prominent horizontal dark streaks on it's forewings. These contain androconial scales, from which pheromones are released during the courtship flight.

 

Silver-washed Fritillary Argynnis paphia, female, Wiltshire, England

 

Females have a similar pattern of black spots, but lack the horizontal streaks. They are normally a dull golden colour, often with a slight greenish tinge. The greyish female illustrated below is the much scarcer and very beautiful form known as valesina. This variety is recessive, and only occurs at certain sites - usually in long established colonies in oak forests.

 

Silver-washed Fritillary Argynnis paphia, female form valesina

 

The butterfly is common and widely distributed across much of Europe, but absent from northern Scandinavia, northern Britain, and the southern parts of the Iberian peninsula. Beyond Europe it occurs in northern Algeria, and is widespread across temperate Asia, reaching China, Korea and Japan.

 

Silver-washed Fritillary Argynnis paphia, male, Alice Holt forest, Hampshire, England

 

The common name refers to the suffused silvery markings on the greenish underside hindwings. These features help to distinguish this species from the European Pandoriana pandora, in which these markings are much more clearly defined.

 

Another similar species is Childrena zenobia, found in China, Siberia and Tibet, which has a conspicuous lattice of silver markings on the underside hindwings. Argyronome ruslana from Korea, Siberia and Japan is also very similar to Argynnis paphia on the upperside, but it's underside hindwings have a broken silver median line dividing the greenish basal area from the reddish outer half of the wings.

 

Silver-washed Fritillary Argynnis paphia, males basking on bracken in early morning

 

Habitats

 

The Silver-washed Fritillary prefers slightly shadier conditions than most other woodland Fritillaries, and has been better able to survive in high canopy forests and in woods that have become neglected and overgrown. The highest populations occur in mature oak plantations where a program of regular thinning encourages a profusion of dog violets to germinate beneath the trees. The best sites are also typified by having glades and grassy tracks where thistles, brambles and other nectar sources are abundant.

 

Silver-washed Fritillary Argynnis paphia, males at bramble, Hampshire, England

 

Lifecycle

 

The butterflies emerge in June and July, and have a life expectancy of about 3-4 weeks, although many are killed by birds before fulfilling their potential life spans.

 

The greenish-white eggs are laid singly in crevices in the bark of oaks, and more rarely on other trees including beech, ash and larch; normally at a height of about 2 metres, on the moss-covered east or north-facing side of the trees. Often a female will revisit the same favoured tree trunk, laying a dozen or more eggs in the space of an afternoon.

 

Immediately after hatching in August, the larvae devour their egg-shells which contain vital nutrients. They then enter a state of diapause, remaining hidden in the crevices of the bark until the arrival of sunny weather in March of the following year. At this time they descend the trees and wander in search of dog violets Viola riviniana. They feed diurnally, eating only the lobes of the violet leaves, and then move on to another plant.

 

The fully grown larvae can sometimes be found basking on dead oak leaves in May or early June. They are black, with a double yellow line along the back, and adorned with dull orange branched spikes on the back and sides. The 2 spikes on the first segment are black, and inclined forward over the head.

 

The slightly spiky pupa is mottled in shades of brown, and decorated with golden spots. It is almost impossible to find in the wild. It hangs by the cremaster from woody stems in shaded situations close to the ground. The pupal stage lasts for about 3 weeks.

 

Silver-washed Fritillary Argynnis paphia, male, Hampshire, England

 

Silver-washed Fritillary Argynnis paphia, male, West Sussex, England

 

Adult behaviour

 

The first males emerge in late June, appearing about a week before the first females. Individual butterflies can live for up to a month, with worn specimens seen as late as early September.

 

Overnight, and during dull weather, the butterflies roost amongst oak leaves high in the tree tops. In the early morning they bask high up until the rays of the sun reach the forest floor, and then drift down to continue basking on bracken, hazel leaves, and other low vegetation.

 

Silver-washed Fritillary Argynnis paphia, male, Hampshire, England

 

As the day warms up they become more active, nectaring avidly at thistles, bramble blossom, lime blossom, hemp agrimony, hogweed and ragwort. They are also often seen imbibing honey-dew from the surface of leaves, or settling on stony tracks to obtain mineral-rich moisture.

 

The courtship ritual of the Silver-washed Fritillary is one of the most endearing and familiar sights of the English summer - the female flies in a straight line along woodland tracks at a height of about 2 metres, with the male repeatedly looping around her, showering her with pheromones. After enticing her into copulation, he carries her in flight to a safe resting place high in an oak tree. Periodically the pair fly down to settle on bracken or hazel, or to nectar at bramble, but return to the tree tops if disturbed. Copulation lasts about 2 hours and takes place in late morning or early afternoon.