"Each web is a functional structure whose purpose is to trap insects. Spiders are the world's most effective control of insect populations-far more efficient and less dangerous to man and other organisms than any insecticide. The spiders traps are marvels of engineering. A basic type of structure is built by each genus of spider, but an individual spider adapts its architectural design and engineering plan to a particular environment. The site determines some of the structural elements. Inconsistencies are based on the outline of the site, on wind direction wind speed, on intervening obstacles, on the amount of precipitation and on other modifying factors. As a result the foundation strands of the webs differ, and the spider spins its standard pattern within varying frameworks.

"Large spans require strong reinforcement, and in windy areas and along shores of lakes I have been able to collect with less breakage because there the webs are stronger than they are in the shelter of deep woods, even though the webs are built by the same genus of spider. Consideration seems to be given to the location that offers the best potential source of food. Lighted windows attract certain insects, and it is across these openings that hangs the 'orb web' spun by the spider Araneus marmoreus [see above]. In the basement of a barn it is around a lone window that the orbs of this spider are strung; in the unlighted areas of the barn I have found only the haphazard strands of the spiders of the theridiid family. In a completely dark basement I have discovered no Araneus marmoreus webs but have seen many sheets spun by theridiids and the orb webs of the nearly blind cave spiders [see Figure 2]. Apparently Araneus marmoreus seeks light and the insects that light attracts. Perhaps this indicates that different families of spiders prefer to eat particular kinds of insects.

"There is a rich variety in the design of spider webs. The design that is literally closest to home is the apparently tangled maze of the house spider Theridium tepidariorum. Actually this irregular mesh is based on a predetermined plan and is a most efficient trap.

"Some webs that are spun on the ground look like small glass carpets when they are wet with morning dew. These are sheets woven into funnels that lead down into the ground [see Figure 3]. Strands of silk are strung above each web; flying insects bump into them and drop into the trap below. Grass spiders (Agelenidae) work throughout the summer perfecting and strengthening their webs, until by fall the webs are at their peak of efficiency and beauty.

"Some spiders (genus Erigone) build sheet webs in bushes and tree branches. These are horizontal platforms with trip-threads crisscrossed above them. The spider waits under the floor and, as insects fall onto the trap, pulls them through the sheet. The rips are repaired immediately, with the result that the sheets last a long time.

"The woods in my locality are full of dome webs spun by Linyphia marginata that sparkle like silken parachutes among the branches of high trees and low shrubs. These are roofed-over sheet webs. The spider hangs under the dome to catch insects that land on top of the dome and also those that are knocked to the floor by the almost invisible threads strung between floor and ceiling [see Figure 4 ].

"The triangle web is a compact, stripped-down structure and an ingenious trap. It is wedge-shaped and has four spokes radiating from a single strand [see Figure 5]. The builder of this neat and simple structure, a member of the genus Hyptiotes, waits on the slackened strand away from the web, and when an insect brushes against the threads, the spider vigorously pulls the guy line taut and shakes the web, thoroughly entangling the victim in sticky silk.

"The most spectacular webs are of course those spun by the orb weavers. The spokes of these webs are dry silk laced with spiral strands covered by viscous droplets. To form and space the drops evenly along the threads the weaver applies a widespread phenomenon of nature: the standing wave. First the spider attaches a thread coated with a thin glue to a radius, pulls it taut and attaches it to the next spoke. Then, before repeating the operation between the next two radii, the line is plucked as if it were a guitar string. The vibration sets up standing waves-evenly spaced intervals of maximum vibration along the fiber that are separated by nodes. The glue flows to the nodal points, where it collects as minute and remarkably uniform droplets.

"The fragile orb webs are often torn by insects, wind, rain and at least one human female web collector, but the patient weavers rebuild as necessary, sometimes as often as once a day. After a driving rain that demolished virtually every web strung among the trees in our woods, I was able to collect samples of early phases of reconstruction within 10 minutes after the storm.

"Sometimes the long guy lines that sustain the orb itself are used by neighboring spiders as mutual supporting strands. It has been established that each spider's world is within the boundaries of its own snare. An orb spinner does not voluntarily leave the confines of its trap and there is no visiting among the spiders. In fact, a trespasser is quickly attacked. An interesting exception takes place during the mating season. During this period a male spider plucks the female's web in such a way that he is immediately recognized and not mistaken for prey.

"Orb webs come in many sizes; the size is in direct proportion to the length of the builder's legs. There are modifications in the hub designs constructed by the different varieties of orb spinners. Experienced observers can identify the builder by its handiwork. The accompanying webs show some typical patterns [see Figure 6].

"My principal technique for collecting webs should be easy for anyone to master. I simply spray the web with lacquer and mount it on a sheet of paper. I trudge through the woods for hours carrying my spray can and searching for the virtually invisible silken traps. My middle-aged eyes require a bit of aid. At each likely web site I don my bifocals and examine what often turns out to be blank space. Staring into empty air at close range makes one feel ludicrous enough, but spraying that air with paint appears even more so to onlookers who cannot discern the beautiful patterns that occasionally materialize.

"There are many ways to collect webs, but with my technique the web is sprayed with a color that will make a contrast with the chosen background for better visibility. The spraying must be done at quite a distance from the web or the jet of air may damage the structure. The color must be built up gradually with several thin coats of fine mist, so that the growing weight of the lacquer does not make the strands sag or otherwise disfigure the structure.

"After the web is colored a sheet of paper or cardboard is placed behind it; the web is composed against the sheet and then the paper is carefully brought forward into contact with the fibers. The long structural strands are cut at the edges of the paper and the web is removed from its site.

"There are a few pitfalls. Smooth paper presents problems; most webs do not cling to it readily. Such paper can be used if the rim of the sheet is sprayed with rubber cement. The tacky border will then catch and hold the radial strands. The instant any structural strands are broken or pulled out of alignment the entire web disintegrates. An other way to assure adhesion to the background is to spray one side of the web with rubber cement before collecting it against the paper. Flocked paper makes one of the best background materials because the nap tends to hold the fragile silk in place. After the web is mounted on its background the entire sheet can be strengthened by spraying with clear Krylon or a similar plastic.

"Even people who abhor spiders acknowledge that spider webs are compositions of remarkable beauty when they are transferred from the corners of rooms and attic beams to backgrounds of color and placed in appropriate frames on walls. Demolishing webs may dismay the spiders, but it does not entirely dishearten them; they promptly rebuild the webs. Webs are expendable but spiders are not, so care should be taken to safeguard the lives of these hardworking creatures.

"It is particularly interesting to study the webs in relation to the species that spin them. At one point in the evolution of arachnology attempts were made to classify spiders by the type of web they weave. Subsequently it was found that some closely related species spin webs of radically different types that some distantly related species construct similar webs. On the other hand, the web spun by a given spider is consistently characteristic of its species even of the age of the spinner. Some adult orb weavers spin webs as large as nine feet in diameter; the young of the species make similar webs that measure only a few inches across. By collecting and cataloguing specimen webs in loose-leaf binders it is possible to follow the growth and development of a species throughout a season. Unfortunately existing collecting techniques preserve specimens in only two dimensions. This works well in the case of orb, triangle and sheet webs. One wishes that a method could be developed for preserving the three-dimensional structures, such as funnel and dome webs, without distortion.

"Pending such a development, I shall continue collecting specimens in two dimensions. As one would suppose, my preoccupation has done little to enhance my reputation as wife, mother and housekeeper. After all, my investigations have put me squarely on the side of the much maligned spider. I have come to enjoy touting it as a benefactor to man and particularly to his wife."

Bibliography

AMERICAN SPIDERS. Willis J. Gertsch. D. Van Nostrand Co., Inc., 1949.

THE LIFE OF THE SPIDER. John Crompton. The New American Library of World Literature, Inc., 1954.

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