NATURE NOTES.

New Zealand Herald, Volume LXV, Issue 19986, 30 June 1928, Page 1 (Supplement)

NATURE NOTES.

GOSSAMER AND WEBS.

BY J. DBUMMOXD, F.L.S.", F. 7.5.

One morning last month many small greyish-brown spiders, about the size of a pin's head, floated in the air, on about three-foot lengths of web. some feet from the ground, in front of Mr. RHoe's house at Tteweti, near Helensville. Several acres of a grass paddock over which they floated were covered with strands of fine gossamer. The previous morning gossamer covered part of the sandhills behind the farm. On a Woodhill farm, closely covered with the gossamer, Mr. Hoc caught one of the spiders, which, sending out about two feet of thread, floated down to the paddock. Almost 40 years ago Mr. Hoe, at Black Spur, South Gippsland, Victoria, saw a member of the same species of spider, or of an allied species, send out a thread and float away on the air. " I would be very pleased to know the position this spider occupies in the scientific world, and something of its habits," he writes.

The gossamer-spider was believed in by old-time naturalists, but it cannot be identified now, simply because the practice of spreading sheets of gossamer over parts of the countryside is followed by a large number of species belonging to different spider families. In every case, apparently, the exquisitely fine, threadlike, filmy substance that floats in the air or covers fields and paddocks, trees and shrubs, is spun by young spiders, newly born. Multitudes of tiny spiders send out their threads. These, intermingling, are carried away by light air currents, and gossamer is made- When the very young spiders swarm the air often is full of the gossamer flakes. They may rise to great heights: they may be carried great distances. Gilbert White, father of English naturalists, one of the most charming of all naturalists, saw a shower, esiimated by him to be at least eight miles long. On every side he beheld " a continual succession of fresh flakes falling into sight and twinkling like stars as they turned their sides toward the sun." When he climbed a hill 300 feet high he did not escape the shower.

On the Beagle's memorable voyage round the world some 95 years ago Charles Darwin, the young naturalist on board, was surprised one day to find that the rigging was coated with the woolly webs of gossamer-spiders. The vessel was off the South American coast, and land was 60 miles away. Vast numbers of a species of small spider, dusky red. about a tenth of an inch long, hung to the webs. Each spider, when it first came into contact with the rigging, was seated on a single thread. The mass of web seemed to be formed by separate threads being On arrival the spiders were very active. One sometimes fell, but ascended by its thread. All seemed very thirsty, drinking eagerly of drops of water. The stock of web possessed by each, apparently, was inexhaustible. T\ a telling some suspended by single threads, Darwin repeatedly noted that the slightest breath of air bore them off out of sight in a horizontal line. When the spiders were placed on an eminence, or when they crawled on to one. each eleI rated its body, sent forth a thread, and j sa iled away, with an unaccountable speed.

A silken thread of gossamer, before it leaves a spicier s body, is a gumrnv fluid. Emitted ;in the most delicate streams, it solidifies as it meets the air, but remains so, very fine that, when gently wafted on the face, or hand, its light touch hardly is felt. A thread comes from a spinneret. Usually it is drawn out by the hind legs, but a spider sometimes attaches it to an object and drops. The spider can stop at will in the descent. Almost everybody has seen a spider drop at the end of a thread, suddenly stop, and drop again. The muscles that close the aperture of the spinneret are weak. By steadily pulling on a thread, a naturalist reeled out yards of silk. The flow was uninterrupted until the spider rubbed its spinnerets together and broke the thread.

Members of a family of small spiders, the Theridiidre, with about eighty species in New Zealand, live among the roots of grass and herbage. A member of this group has been seen to cease its wanderings, turn its head in the direction of the wind, raise the front part of its body as far as its legs permitted, and elevate its body. Streamers of silk have been seen coming from its spinnerets. The silken streams are shot out for a short distance. The current of air draws them out further, until they may extend for several feet. The spinner feels the pull of the threads. When the tension is sufficient, it lets go its hold on the fence or other object to which it has climbed. It vaults into the air, and away it goes. When there is a false start, and the insufficient- buoyancy of the streamers causes the spider to descend quickly, a fresh start is made.

These " stunts" explain the marvellous silken carpets disclosed by the dew at some seasons on lawns and fields. From early dawn young spiders have crawled over the grass, climbed the higher blades and let themselves sail in tlie air. A member of another family, the Attidas, was followed by an observer for fifty feet. It then was wafted upward in a current of air and disappeared from sight. A garden spider, in the same way, sailed over a field and a hedge, crossed a road, and came to a rest on the top of a tree. This ballooning is accepted as a probable explanation of the wide distribution of some species of spiders that do not seem adapted for travelling long distances.

The orb-web, or wheel-web, which excites admiration, is the work of the geometric spider, of the family Epeiridre. One of (hese spiders first sends out the foundation threads that will form the boundary. The spinnerets are separated and are rubbed against one of the points of attachment. Walking away, the architect trails behind it a thread which, by the use of one of its hind legs, it keeps free from neighbouring objects. When another point, of attachment is reached, the line is made taut and is fixed by rubbing the spinnerets against it. In this way a frame is made for the orb or wheel. The process of fixing and drawing out a line has been watched in the case of a spider in a glass vessel. The use of a lens has shown that many fme lines start from the point of attachment, and, as the spider moves away, seem to merge into a single line.

Orb-webs often bridge gulfs impassable to the spider. They often span streams. In these cases again the help of air currents is sought. An Epcirid spider placed on a stick that stood upright in a vessel of water could not escape when there were no draughts in the room. Air currents carry the silken streamers across water, and the streamers are entangled in objects. The spider then hauls the line taut, tests it by gentle pulls, and, if it is satisfactory, walks across liaiid over hand, ; in an inverted position, carrying a second line to strengthen the first one. The spider has only to cross, attach the thread, and carry it back to the base. A circular web is made between the two lines. In England bridge lines eleven feel long have been measured.