The red admiral’s admirable fortitude

Outdoor Living

ART ON THE WING A red admiral encountered on the Clogher Bog Loop Walk. Pic: Michael Kingdon

Country Sights and Sounds
Michael Kingdon

A light morning mist left the world covered in dew, beads of which sent colours shivering and sparkling across the bog. A few late flowers cling to life, albeit rather tenuously. The rich gold of sow thistle brightens one small sun-warmed corner, where bumblebees work while they can. They lift from starry sun to starry sun probing deep for little reward, while a little way beyond hoverflies and honeybees work over blossoming ivy.
There came moments of real warmth around midday, when we could nearly dream ourselves in summer once more. When a newly emerged red admiral (Vanessa atalanta) settled first on reddening leaves of bramble and then on the gorse which lines the narrow path, summer’s loss was soon forgotten.
Vanessa would be very much at home in the tropics, where everything is bright and filled with colour. But no, it is one of our own. It was born here, though by what mischance we cannot say, for the life of the red admiral is one of wonderment.
Its parents were likely first generation Irish, the grandparents perhaps not. Every spring, in lands to the south of the great Alpine range of mountains, red admiral butterflies begin to emerge from hibernation. Making use of powerful updrafts of warming air they rise skyward, ready to follow the sun to the north.
A favorable wind carries them over rocky heights and speeds them on their way. Some settle a short distance from where they set out. Others spread across continental Europe before settling down to breed. A few fly the English Channel and then the Irish Sea. Travel-worn and exhausted, it might be all they can do to deposit a few eggs, each the size of a pinhead, on the leaves of those stinging nettles we left growing along the ditch.
The eggs are near as pretty as the insect itself. Like miniature water melons, they are; lime green and longitudinally ridged, until we examine one with a hand lens. Then it becomes a miniature work of art, carefully shaped, perfectly formed, and quite startling in complexity. All red admiral eggs are similar, while those of other butterflies are just as beautifully composed though of a different structure.
We shall stick with Vanessa for now. Her eggs are laid singly, on the surface of suitable leaves, in this country mostly on nettles. Within five to seven days a tiny caterpillar emerges from each egg and immediately devours the shell of what had been its home. Then, as if instructed, it builds itself a tent with the leaf on which it was born, using multiple strands of fine silk to bend everything into shape. And here it will live, along with a number of companions.
These are not happy housemates. In times of drought or food shortage they will merrily make a meal of their siblings. They can also enter a state of suspended animation until more favourable conditions return and development can be resumed.
Remarkably, caterpillars actually grow inside their skin rather than have it grow with them. Once they fill their old overcoat they gulp air into their body, which causes them to swell and their skin to split. Then out they climb, wearing a slightly oversized, loose fitting jacket which they must work hard to fill.
And for a caterpillar working means eating. On average, each of the red admiral caterpillars will eat five times their own weight every day. After a three week binge they weigh a colossal one thousand times their birth weight. To illustrate the growth rate, imagine a three kilogram human baby drinking twenty litres of milk on day one. Three weeks later the same child weighs over three tonnes.
At the fifth instar, or development phase, something strange happens. Instead of finding another soft, pliable skin beneath the one thrown off, the caterpillar has a hard, almost bony structure, inside which metamorphosis, which involves chemically dissolving and rearranging the organs, will take place. In a warm climate pupation is short, and the new butterfly might emerge after only a few days. Here in the west, where temperatures rarely exceed 18ºC it might be two months before Vanessa is finally able to spread her new wings.
The insect pictured is newly emerged. It will not survive an Irish winter, although recent research has shown a few may hibernate successfully in the south of England. This one might attempt a return migration to where her predecessors set out last spring.
What a brave and beautiful creature Vanessa truly is.

Michael Kingdon formerly wrote these columns under the pseudonym John Shelley. A naturalist and keen fisherman, he lives close to the shores of Lough Carra.