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Butterfly Focus

Species Focus : Speckled Wood [Pararge aegeria tircis]

Male Speckled Wood, August. ©J.Harding.

Male Speckled Wood, April. ©J.Harding.

The Speckled Wood may appear to be an unremarkable and common butterfly that hardly rates a mention. It occurs throughout Ireland, most of Britain and Europe but avoids most of Scandinavia and Northern Russia.

It was not always so successful in Britain and the old Irish records are too few to be certain of its past status here. By the 1920s the butterfly had disappeared from most of its former range in Britain. From then it began to recover and is now re-colonising the border with Scotland after an absence of nearly 150 years. It is still absent from most of Scotland where it occurs mainly in the west. Its spread in Britain is attributed to increased temperatures and woodland management changes which have seen a huge decline in coppicing and increased shade. While these changes are harmful for fritillaries the Speckled Wood is our most shade tolerant butterfly and benefits greatly.

The Speckled Wood is the only butterfly in Ireland and Britain that is able to over-winter either as a caterpillar or as a chrysalis. This explains why the first brood that emerges in spring and early summer lasts so long although the adult butterfly is short-lived. The first butterflies that we see, usually in April, emerge from over-wintering pupae and these overlap, in June, with those that over-wintered as caterpillars.

A gap occurs in the flight of this species during July but towards the end of July lasting well into September there is an extended emergence resulting from larvae produced during April-June. Not all of the spring-time larvae produce second generation butterflies; some develop slowly and form over-wintering chrysalises in autumn.

A smaller third brood flies in late September and early October resulting from the second brood. Not all second brood’s larvae develop at the rate needed to produce third brood butterflies; these caterpillars will over-winter as pupae or larvae while the third brood’s offspring will probably pass the winter in the larval state. This is not a universal rule as warm conditions and lengthy sunlight may result in some of the third brood producing pupae before winter. The research suggests that the individual Speckled Wood larvae vary greatly in their response to light and temperature. This variability explains the complexity of the brood structure and adds to interest in this species.

The adult butterfly also behaves differently depending on the time of year, the time of the day and temperature. Males find mates using patrolling and perching strategies. Patrolling an area of woodland edge, clearing or hedge may increase his chance of encountering a female but it also requires much more energy, requires higher temperatures and increases the likelihood of predation. Patrolling may mean less territorial behaviour resulting in fewer fights with other males. Cooler spring and morning temperatures favour perching over patrolling.

Fascinatingly, there is some evidence that some males are more anatomically suited to one mate-seeking strategy. Perching involves a male selecting a sunny area such as a sheltered area of shrubbery, a woodland edge or glade and waiting on a leaf and sometimes on the ground. Sometimes this perching male will undertake an occasional inspection of his territory before returning to his perch. Any male who enters the territory is attacked and males spiralling in close circles are a common sight in sunlit clearings during the summer.

Virgin females advertise themselves by flying 1 to 1½ metres above ground around shrubbery. [Mated females will be seen fluttering around and landing on tall grasses growing near shrubbery].A perching or patrolling male soon engages the female by fluttering around her. The female leads the male up to a high point on the tree [3 ½ metres high in the examples I observed] where the male flutters briefly around the female. He settles and positions himself facing away from the female, moves towards her and pairing occurs. Both sexes close their wings before joining but during one courtship I saw both with wings fully open when first settled on the mating platform. The pair in copula remains high up on the tree unless disturbed. The courtship lasts about 30 seconds and one observed mating lasted just 20 minutes.

A seasonal difference exists in the egg laying sites chosen by females. Early and late in the year sunny, warm clumps of wild grasses are selected for oviposition while during the summer heat more shaded, lusher grasses are selected. Seasonal dimorphism is also a feature of this familiar yet intriguing butterfly. The spring hatch from over-wintered pupae contains larger, richer cream markings on their upper surfaces than later emergents; these differences can be seen in the photographs.

Finally, one of the benefits of the Speckled Wood being so easily identified and widespread is that it is easily observed and its uniqueness appreciated. Scott Simons who has contributed his take on the Speckled Wood became interested in butterflies when his wife heard Eugenie Regan talking on radio about the butterfly recording scheme run by the National Biodiversity Data Centre. An adventure of learning followed that brought their familiar country lanes into an entirely new and fresh focus. Scott is now managing part of his garden for butterflies. Enjoy Scott’s interpretation of the Speckled Wood.

SPECKLED WOODS

By Scott Simons.

Beauty is hard to describe. But, we all know it when we see it. Ireland is a beauty.

There are, however, distilled essences of Ireland, places and things that are special, even amidst so much ‘ordinary’ perfection. High mountain streams gurgling over rocks and drops midst heather and wild flowers. A splendid song in a snug country pub. Butterflies with wings spread, resting on a cabbage so they can deposit their spawn to eat the heart out of your future dinner.

No. No. Those are Cabbage Whites, a wide class of flutter-bys that actually compose several very distinct species. This week’s butterfly of choice is the Speckled Wood. Actually, it chose itself by becoming the most widely dispersed butterfly species in Ireland.

That’s what surveys from 160 volunteers throughout Ireland reported in 2010. These volunteers walked their one to two kilometre transects once a week and this is what they found. Speckled Woods. The Speckled Wood was seen in 134 of these scattered viewing sites. They are widely dispersed but not, however, the most numerous species. That honour belongs to Green-veined White.

You’ve probably seen some Speckled Woods of your own. They are a fine brown species with cream dots around the perimeter of their wings. These little beauties like dappled sunlight so our country lanes and hedges suit them perfectly. Their name describes both their habitat and decoration.

THAT EXTRA KICK

The Speckled Wood drinks the hard stuff. Flowers just don’t have enough kick, though they have been spotted occasionally feeding on bramble flora. What really revs their engines is aphid honeydew. The Speckled Wood looks for an aphid restaurant – your roses – and cozies up to the insect till it secretes sugary sweet nectar. Then the butterfly unfurls its proboscis and laps up this high octane liquid.

THE GUYS

Having drunk its fill, the Speckled males’ thoughts turn to the ladies. One interesting thing about the Specklies is that the males are territorial. They stake out an area they think will attract a female. This butterfly equivalent of a shoe store is usually a sunny glade replete with attractive spots on which to perch. Bramble bushes, fence posts and hawthorn hedges do the trick nicely. Then the lads adopt one of two strategies; they let the females come to them, or actively hunt them down.

The quiet ones sit on their perch till they spy a suitable prospect blundering through the specially chosen glade. The hunters patrol their sunny territory, back and forth, actively looking for that elusive someone. Think butterfly disco. And if two males desire the same territory, they fight. A butterfly bout consists of the two hormonally charged boyos circling round and round and batting each other with butterfly wings.

THE GALS

The female Speckled Wood is a rather doting mother. She flutters around Cock’s-foot or Couch Grass and when she spies the perfect piece of grass, she lays one, and only one, bun-shaped yellow egg on the underside of a leaf. She wants no crowded table where her offspring will have to duke it out for a nice piece of grass. Each young’un gets its own dining room and kitchen. And Mom’s careful enough to find shaded spots in the summer and sunny ones in the spring and autumn for her little precious. Having found one perfect spot and done the business, she’s soon off to oviposit her next egg.

SPEED IS THE ESSENCE

This careful mothering results in up to three distinct generations each year. Speed is the essence. That lone egg takes two weeks to hatch into its first instar, that is, into a small caterpillar. Eating grass, grass and more grass it reaches full size in a month. The caterpillar then spins its pupa on a grass stalk or low down on a stone wall. This lovely apple-green tent is home for four weeks. That’s two and a half months from egg to butterfly.

The autumn hatch find themselves growing up in an increasingly cold and forbidding world. There aren’t many aphids around in late October. Denied a bit of the rare oul’ stuff, this last generation hibernates till the world warms and the aphids again hang out the Open sign.

Speckled Woods – not your average butterfly!