Shape-Shifting Animals on an Inhospitable Planet

Lizards’ feet are morphing, squid are shrinking, butterflies’ wings are growing stronger.

- Rebecca Giggs

In June of this year, not long before the midwinter solstice, catastrophic floodwaters draining from the Gippsland Plain, in southeastern Australia, left in their wake an otherworldly phenomenon: Translucent spider silk, extending half a mile in some places, trailed over riverbanks, roadsides, and fields, rising into glistening spires atop highway signs and shrubbery. On once-humdrum stretches of road, drivers pulled over to stare, take pictures. When a breeze ran through the membrane, it rippled with the fluency of a tide surging in a mangrove swamp. Light trembled on the sodden turf beneath. How improbable that something so delicate, sensuous even, might remain after something so destructive.

To spot the creatures responsible, you would have had to draw close. Sheet web spiders—constellations of them—clustered in a cosmos of their own froth and protein. A mature sheetweb is rarely bigger than a contact lens; the spiderlings are best made out with a magnifying glass. On days of ordinary weather, millions live in the earth, but when threatened by inundation, the spiders abandon their belowground niches. Each fashions a single thread, a streamer, to function as an emergency airlift. Lofted up by atmospheric currents, and possibly by electrostatic crackle too, the spiders sail on the tips of their lines toward higher terrain, alighting, in time, on fence posts or treetops or ascending farther still. In 2011, a pilot reported crossing paths with clumps of spiders at 2,000 feet. In a departure from habit—wingless as they are—the sheetwebs fly. The tracers of their mass decampment, a strand of silk for every spider, settle on a scale so vast, so uniform, the result looks less like the work of animals than like something mythological or architectural: a mysterious Christo at work, festooning the landscape.