Species of the day: Marbled White

11 July 2020 | Posted in James Duncan , Insects
Species of the day: Marbled White
Marbled White © Bob Eade

By James Duncan

Learning and Engagement Officer

The naming of the Marbled White (Melanargia galathea) would logically lead you to assume it as a member of the 'White' butterflies. Rather confusingly, and despite its colouration, it does in fact belong to the subfamily Satyrinae, closely related to butterflies known more commonly as the 'Browns.' These get their name, the Satyrids, from a pair of sharp points at the end of the caterpillar's body - thought to resemble the ears of a woodland deity known as a Satyr in Greek mythology. Looking like a cross between a fashionable lampshade and a chess-board, the almost monochrome colouration of the Marbled White doesn't stop it from being one of our most exquisitely patterned butterflies. This is in marked contrast to its typically more sombre relations, it being the real exception to the rule. One feature they all share is the presence of 'eye-spots' on the wing margins, a feature used as a distraction technique to startle would-be predators, though once again the Marbled White differs in having them only on the underwings. Like the others in their extended family, Nymphalidae, their front legs are reduced to a pair of brush-like appendages so ultimately they walk on only four of their six legs. 

The Marbled White will normally indulge in a spot of early morning sunbathing in an effort to warm the flight muscles, making this a useful time for easier observation. However, when the sun's blazing they're at their most active, always on the move, showing a marked preference for nectaring upon the purple blooms of KnapweedsThistlesScabious and Marjoram. The males tend to flutter about rather ceaselessly, determined to hunt down a receptive female at which point he'll dance around her, releasing pheromones from scent scales on his wings to stimulate her interest. Once mated, the Marbled White has a rather haphazard approach to egg-laying whereby the female scatters them at random in some kind of aerial bombing run. Fortunately she doesn't need to be too precise as the caterpillars favour a variety of grasses for food, including Red FescueCock's-foot, TimothyTor-grass and Yorkshire-fog. Initially they have a somewhat relaxed approach to feeding and having devoured their own eggshell immediately enter hibernation until the spring. Pupation is similarly relaxed in style, often occurring loosely upon the ground or within the grasses, with no attachment to stems - admittedly the pupae usually display effective colour camouflage.   

Now is the perfect time to head out and spot a Marbled White, for the flight season of their single brood typically runs from mid June to mid August. We're also rather lucky in the south for their habitual preference is that typified by the South Downs - chalk downland. There's little doubt its distribution is markedly more centred around the south of both England and Wales, though it is now commencing a gradual expansion northwards, perhaps owing to the warming effects of climate change. Though calcareous soils are certainly preferred, the Marbled White may now be found on almost any areas of wildflower-rich unimproved grassland, even though the colony sizes will be significantly lower. Upon their favoured chalk, competition for resources can be quite intense and you might spot a single flower head with several adults competing for feeding space. The unmistakable beauty of the Marbled White certainly provides a quintessential ingredient of a summer's walk on the South Downs, where you can see them at a number of our downland reserves. 

Marbled Whites mating © Bob Eade

Marbled Whites mating © Bob Eade 

Comments

  • Gordon King:

    20 Jul 2020 21:33:00

    Last tueday at Nepp, I held a Purple Emperor with my daughter Elaine & a really nice expert named Bill who has written a wonderfull book &took many photo’s of this rare butterfly. GR8.

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