sanctuaryofwings
Marbled white (Melanargia galathea), a species in the family Nymphalidae.
Photo: Didier Descouens · Wikimedia Commons · CC BY-SA

· · Last updated

Contents
  1. Identification
  2. Range and habitat
  3. Life cycle and host plants
  4. Behaviour and flight period
  5. Similar species

The marbled white, Melanargia galathea, is a butterfly of the family Nymphalidae, instantly recognisable by its chequered black-and-white wings. It belongs to the subfamily Satyrinae, the browns, though its colouring sets it apart from every one of its mostly brown relatives. The species occurs across most of Europe, southern Russia, Asia Minor and Iran, with an isolated population in Japan, though it is absent from Ireland, northern Britain, Scandinavia outside Denmark, and Portugal and Spain, and within Britain it occurs in colonies south of a line running from Glamorganshire in the west to north-east Yorkshire in the east, though it is absent from much of eastern England, Scotland, Ireland and the Isle of Man.

Identification

The marbled white is a medium-sized butterfly, with males reaching a wingspan of about 53 mm and the slightly larger females about 58 mm. Both surfaces of the wing carry the same bold black-and-white marbled pattern, and on the upperside each wing shows an oval white spot that is not divided by a dark bar, a detail that helps separate it from its continental relatives. The underside is paler, light grey or light brown, with a row of small grey eyespots on the hindwing. The sexes look much alike, though some females show a faint yellowish tinge on the underside. In Britain the pattern is so distinctive that it cannot be confused with any other species found in the British Isles.

Range and habitat

The marbled white favours unimproved, flower-rich grassland with grass up to about 0.5 m tall, a habitat type that in Britain includes downland, road verges, field margins, woodland clearings and disused railway lines, with its largest colonies found on chalk and limestone downland. Further afield across its European and Asian range it also turns up in forest clearings and edges, meadows and steppe, up to elevations of 1,500 to 1,700 m. In Britain its range has not stood still: the species saw its UK range expand during the late twentieth century, a shift consistent with a butterfly tracking a warming climate into grassland beyond its historic stronghold in the south.

Life cycle and host plants

Caterpillars feed on a range of coarse and fine grasses, including cock’s-foot, red fescue, sheep’s-fescue, Timothy, tor-grass and Yorkshire-fog. The female has an unusual way of laying: rather than attaching an egg to a leaf, she drops it while perched on a grass stem or in flight, scattering eggs loosely through the sward. The egg stage lasts around three weeks before the caterpillar emerges and eats its own eggshell before settling down. It then overwinters as a first-instar caterpillar without further feeding, tucked deep into a grass clump, resuming growth through four instars the following spring. The caterpillar occurs in both green and brown colour forms, and pupation happens on the ground, where the chrysalis forms loose among leaf litter or moss, without attaching itself to anything, and lasts around three weeks before the adult emerges. The species completes a single generation each year.

Behaviour and flight period

In Britain, adults are on the wing through the latter part of June, reaching a peak in early July. On cool mornings a marbled white warms up by holding its wings open to absorb the sun’s rays, and once active it gathers at nectar sources, with several adults often competing for space on the same flower head. In poor weather it simply rests, clinging to a grass stem until conditions improve. Many individuals carry small red parasitic mites, Trombidium breei, though this parasitism does not appear to affect the butterfly in any way.

Similar species

Related