Another Life: Pennies from heaven and the secret life blowing in the wind

Twice between the house and the polytunnel I found my face stroked gently by invisible things in the air. On such a balmy autumn day I knew them at once as strands of gossamer, with a couple of tiny spiders at the ends. Even a sometime arachnophobe like me can’t mind the caress of an aerial voyager, a couple of millimetres long, whose landing – on one’s left hand, is it? – might bring some money or luck.

It brought back a good memory. I was crouching on a hillock over at the far lake to enjoy the whooper swans, newly arrived for winter, dipping their necks deep for waterweed. Beyond them was the cliff, brilliantly rimmed by the sun at midday, so that, backlit against its darkness, their beaks came up dripping diamonds. Then I noticed, high above the water, hundreds of shining gossamer threads, hanging almost vertically in the still air sheltered by the cliff. It was a revelation of the secret life in the wind.

In northern Europe it’s mostly the Linyphiidae family, the little “money spiders”, that go ballooning like this, along with young spiderlings of the Lycosidae, or “wolf” family, which don’t sound as friendly. They perch on tiptoe – eight tiptoes, I suppose – on a high point, perhaps on a fence post, to catch the wind. Then they squeeze out silk threads, typically half a dozen, from the spinnerets in their abdomen. Entomologists have differed on whether they let the wind keep tugging the threads out or if the spider anchors them first and pays them out in stages. When they are long enough for lift-off, perhaps a metre or more, up the spider goes.

Charles Darwin, watching this in South America, thought the threads glittering in the sunshine "might be compared to diverging rays of light; they were not, however, straight, but in indulations like films of silk blown by the wind." Aboard the Beagle he found thousands of small red spiders in the rigging when the ship was still 100km off the coast of Argentina.

Almost entire populations of spiders, young and adult, can be prompted to leave home, given the right conditions and pressed by food shortage or overcrowding. In one remarkable experiment, at a sewage works in Birmingham in 1980, dispersal was closely measured for a week after two filter beds were deliberately dried up. The spiders, bereft of flies, climbed bicycle spokes planted in the gravel and took off in their millions. (You can download a PDF here.)

The balloonists can rise to great heights. An antique biplane in the United States sampled them at up to 4,500m, its struts sometimes webbed with gossamer on landing. The naturally descending and discarded strands, tangled by trees, can bring spiders as food for birds. (In conifer forests goldcrests are specially fond of them.)

Other fallen flights of threads, catching beads of dew or mist, can set grassland gleaming. An early letter to “Eye on Nature” came from a Dublin reader, reporting on his discovery in the Phoenix Park one morning in December: “an infinity of strands of silk stretched upon the grass as far as the eye could see. Close by, they shimmered in the sunlight like a moonlit sea . . .”

The life of the “aeolian zone”, a term first used in the 1960s, can still be deeply mysterious. The finding of tiny invertebrates such as bristletails and springtails on Arctic glaciers and of jumping spiders high on Everest, together with a steady rain of dead insect food of all kinds, speaks for the global uplift and wilfulness of winds.

Along with such casual vagrancy are the annual migrations of Ireland’s insect world: the sometimes astonishing comings and goings of hoverflies, dragonflies, moths and butterflies, following migrating birds.

Among the wind’s lighter debris are spores of ferns that may well have brought to Ireland rarities such as the Killarney fern, more at home on the misty slopes of Madeira and the Azores. Such spores share the sky with the pollens, minute seeds, fungi, bacteria and viruses that circulate above our heads.

In 2012 some climate scientists suggested that Kawasaki, a disease causing aneurisms in infants, might well be blowing high across the Pacific from central Asia to infect children in Hawaii and North America. Influenza, too, might be carried in this way.

The part winds played in the postglacial colonisation of Ireland remains obscure and largely unexplored. Sorting out our native plants from the almost equal number of aliens brought in by human activity has been a full-time job. The potential of wind to seed barren landscapes fertilised from the sea by the droppings of nesting seabirds informs a fascinating, illustrated study of the vegetation of Surtsey, Iceland's new volcanic island. (You can download a PDF here.)

Michael Viney's Reflections on Another Life, a selection of columns from the past four decades, is available from irishtimes.com/irishtimesbooks