Lyall Watson – Heaven’s Breath
Every once in a while, when conditions are just right, usually in the spring or the autumn with a gentle breeze or updraft in otherwise still air, the largest and lightest canopy in the world is erected in California. It is almost 2000 metres wide and it soars into a diaphanous, but mighty arch 1200 metres high over Sentinel Rock in Yosemite national park. Sometimes there is another, slightly smaller awning stretched right across Bridal Veil Falls. And both of these are made in a single day by millions of little vagabond spiders. Prompted by subtle environmental cues, involving temperature, humidity and the degree of crowding, great numbers of spiderlings at certain seasons, get a common urge to travel
Spiders were caught at every altitude from 10 to 4,500 metres, with concentrations at 60 and 300 metres which may have been due to a natural weather or thermal ceiling at that level on those particular days. The loftiest catch of all was a sheet-web weaver of the genus Linyphia taken at 4,600 metres, but given the fact that spiders jump about in the Himalayas at 6,700 metres, it is likely that there are other eight legged astronauts floating in the air a great deal higher still……………..
Most spiders in flight are predictably young ones off on their first great migration, but all collections include a number of specimens that are fully adult. Which suggests that taking to the air may be something that spiders do more than once in a lifetime, and usually by design.
The definitive study of spiders in flight remains to be made, but the little evidence we have suggests that the creature suspended beneath its gossamer balloon may be very much in control. By reeling in one or more of the parachute threads, a spider can regulate its descent and might, with the help of such a spider spinnaker, even be able to steer. If the wind rises he can reef in his thread to shorten sails. If the wind drops he can pay out again like a yachtsman… his own body is his craft and crew. And there is nothing except hunger to stop each sailor voyaging on for thousands of kilometres even across whole continents and seas. There is a tendency, even among biologists, to belittle spiders as ‘drifters’ and to label their travels accidental or inadvertent, but this does them an injustice. The winds may determine their general direction of travel, but few, if any of them are transported passively like leaves or dust