Nature 2020 August

Three Butterflies all in a spin

Earlier this year I read that since 1940 over two million acres of the British countryside has been lost. This has been attributed to industrial development, urban sprawl and agricultural intensification. Most damaging, the report concluded, had been the loss of 97% of wildflower meadows.

Many insects species are dependent for their survival on the reliability and diversity of flowering plants that appear at different times across the whole season. On top of this climate change is also impacting by stretching the seasons at either end. Until relatively recently the widescale use of pesticides which could not discriminate between their intended targets and harmless invertebrate species has had a devastating impact on populations. Diseases introduced from abroad by European cousins have weakened the health of our native species.

Measures taken to conserve habitats over the last twenty years have gone some way to stem the impact on insect populations. However there is still a long way to go if ever before we see this decline reversed.

From a young age when my father and I bred butterflies and moths for release I have had a particular interest in the habits of both. Spending so much more time in the garden this year and closely observing butterflies at rest and on the wing have reminded me of the distinctive flight movements of different examples of some of our more common local species.

Despite the very different appearance and habit of three butterflies; the Small Skipper, the Speckled Wood and the Red Admiral.

Small Skippers are fasted flying butterflies you are likely to encounter around here, though a similar-looking close relative the Essex Skipper is also present. Small dark orange / ochre butterflies with sweptback wings when at rest giving them almost a moth-like appearance. Male Small Skipper butterflies have clumps of hairs on their hind legs which they use to deploy a aphrodisiac when engaging in courtship. Standing guard on a suitable grass stalk males will aggressively defend their territories, Often you can see pairs of male Small Skippers spiralling upwards as they engage in aerial combat with the male whose territory it is usually seeing off a challenger.  So obsessed are male Small Skippers with protecting their territories that they will in fact confront much larger butterflies of other species which stray into their patch. Females lay single eggs on grass. The caterpillars hibernate soon after hatching enclosed in a sheath of grass wrapped in silk known as a hibernaculum. In the spring the caterpillar eats ravenously and after a short period pupating they complete their cycle when the adult butterfly emerges in late Spring.

Taken at face value the Speckled Wood butterfly is a very different beast to the Small Skipper. In contrast to the sweptback moth-like appearance of the Small Skipper the Speckled Wood’s design is very much out of the traditional mould of four-winged butterflies. It enjoys inhabiting woodland edges and rides, hedgerows and gardens. Colouration, mid brown and buff coloured with cream ocelli (eyespots), which is why it was in the 18th century known as the Enfield Eye, where it was first identified, and also as the Wood Argus after the many-eyed hero of  Greek  methodology. This disruptive camouflaging, which varies across different regions of the British Isles, provides excellent opportunities to remain concealed where dappled sunlight falls on brown earth. But do not be deceived by the Speckled Wood’s delicate appearance. Just like the Small Skipper the Speckled Wood is another butterfly that displays similar aggressive behaviour and will protect its territory from all-comes including anyone following a footpath that traverses their territory. The male butterfly will vigorously defend its patch. They will engage with any invading males resulting in an upward spiral tussle for dominance. For some time it has been known that the size of left and right wings for some butterflies differs by a few millimetres. Research a few years ago concluded that male butterflies displaying an element of wing-asymmetry allows them to turn faster affording them an advantage in territorial disputes over more symmetrically-winged males. Like the Small Skipper it favours various grasses for a food plant. There are up to four generations per year. Whereas the first three generations of caterpillars reach maturity in a month the autumn generation of caterpillar remains semi-active throughout the winter feeding when it is warm enough and taking up to a further nine months before the adult butterfly emerges.

The third of the British butterflies in this trio which needs little introduction is the Red Admiral. Somewhat of a flag-bearer for all our native butterflies. In the 18th century known just as the Admirable and also the Alderman as its wings resembled the robes of dignitaries such as nobles or liverymen. We rely on migrants from the continent to bolster the Spring population which firs appear in May with a second generation in July and up to two further generations in a good year. Autumn emerging Red Admiral butterflies are strongly attracted to rotting fruit, like fallen apples, and will stubbornly hold their ground and will squabble amongst themselves and wasps like vultures over a carcass. There is growing evidence that some Red Admirals survive the Winter by hibernating. Eggs are laid sparingly on nettle and occasionally hop. The larvae spin silk webs to create protective tents. Like the two previous butterflies it is highly territorial. It is equipped with large powerful wings and like the Small Skipper this makes it a fast flyer. In common with both the Small Skipper and Speckled Wood it employs similar tactics. Male Red Admirals state out their territory and identify a location on which they will regularly perch. They will frequently patrol the whole area with a series of defined routes which criss-cross the territory, returning at the end of the sequence of flights to their original perch. If a rival male is encountered during this reconnoitring the defending male rushes towards the rival from beneath forcing it to fly upwards and then it chases it in an ever-rising and widening spiral until the rival turns tail and escapes from harassment.

Hoping for plenty more warm and sunny days to get out and identify butterflies by their unique behaviours.