Web Wonderings

A spider begins spinning its web by crawling up to some choice vantage perch and reeling out a test line—a sticky silk thread that a breeze will carry to a distant stationary object, to which the silk adheres. Once the far end of the line sticks to something firm, the spider slides down the silk, thickening and strengthening it as she goes. This strong line then becomes an anchor thread that will later support the web, after the spider similarly constructs a couple of other anchor lines.

It's a rather haphazard process, as the spider cannot control where the opposite end of the anchor lines will attach. Thus, the orientation of the web is determined more by fickle breezes that waft through, rather than the intent of the spider.

Smart, successful spiders try to establish their webs in locations where many tasty insects will be flying—to be suddenly trapped in the silky snare. I would assume that evolution has taught a web spider to pick a high traffic zone—otherwise it starves. I doubt that evolution, however, has yet endowed spiders with ways to manipulate the wind, so there is a definite degree of chance to the process. Specifically, the orientation of the web is not within the spider's purview. 

 

So even a smart spider may end up fashioning its web in a direction that has little chance of capturing many bugs. For example, I am sitting in my outdoor tub tonight, looking above me, and seeing a spider's web that is nearly flat against the wall. I don't think that many insects will be intending to fly into the wall tonight, so this web strikes me as one that will see minimal bug traffic. Had the breeze blown that first anchor line in another direction, the spider may have been able to orient its web perpendicular to, or protruding out from the wall—much more likely to snare passing insects. Ahh... the vagaries of the wind.

Another intriguing aspect of spider webs I often ponder is the fact that birds can see into the ultra-violet (UV) range of the light spectrum, and since a spider's web reflects UV light, a bird can see the web and avoid flying into it. This capability is an advantage to both the bird and the spider: the bird doesn't get its feathers coated with sticky silk goo and the web is not destroyed. So if birds have UV vision, I wonder why some insects—locked into a perpetual evolutionary arms race with spiders—have not also developed UV vision. There's another area of research for someone.

(As an aside, a recent development in window construction is to glaze windows with a UV-reflective coating. Birds are far less likely to fly into these windows and kill themselves, because they see the glaze and it stops them, but humans cannot see the coating and thus view the window as transparent. And some of us walk into them.)

Yet another web wondering I have: As I walk through the woods in summer, along the many paths I have created, I keep wandering through spider webs and having them splay themselves across my face or along my bare arms. I'm constantly struggling to wipe off these sticky structures. It can cause a pleasant stroll through the woods to degenerate into a yucky dance, in which I'm striving to wipe off web particles that I can't even see. I hate to destroy a carefully-crafted web, but I can't see them—not having been blessed with UV vision like birds.

This makes me ponder the fact that many of my paths that wander through the woods are also used by deer, since they are smart enough to see that it's easier to follow my paths than forge their way through the tangled underbrush. Deer must also at times find themselves wrapped in spider web strands. How do they deal with it? Does it irritate them as much as it does me? Might they get distracted by the damn spider webs and lose crucial alertness to their predators?

I would be grateful if deer were as tall as I am, since they would then clear out many spider webs for me and make my walks nicer—but they are just not tall enough to sweep away the webs at my face level. They're too short. Hmm.. I wonder if I could breed deer with giraffes, to create a tall, long-necked deer, that would clear out spider webs for me. That sure sounds like another kind of ground-breaking research that would benefit mankind... at least this man.

Wonderful Web—Part 2

Once the web is completed, the builder will settle in to waiting—one leg lazily draped across a thread, so when an insect splats up against the web and tries to struggle free, the vibrations will alert the spider to charge out and secure dinner. The type of web that we humans are most familiar with are called spiral orb webs—simply gorgeous creations, made by (guess what?) orb spiders. Other kinds of spiders spin what are called tangled, funnel, tubular, and sheet webs. (See photos, previous posting.)

I contentedly gazed at this spider as it wove its miracle. I could see it zip in and out, building the radials after the anchors were strong, and then it moved in ever-widening circles, as it added the spirals. As long as this web stays in use, we call it a web. When (and if) it becomes abandoned and collects dust, we call it a cobweb. I wonder what names the spider uses.

I am very grateful for spiders building their webs around here and snacking on insects. The populations of other insectivores—bats and songbirds—are dwindling, so we value every spider’s contribution to check insect overpopulation. 

In mid-to-late summer I run into many spider webs during my walks through the woods. It’s rather irritating to be enjoying a hike and suddenly feel the threads of a web wrap around my face, stick in my beard, or slither along my arms. The sticky threads cling stubbornly to me and the strong anchor threads almost threaten to trap me. In self-defense, I have taken to carrying a small branch with many twigs splayed out at its end. As I walk along, I wave the branch ahead of me, to intercept the webs before my nose does—looking like a defrocked, bearded priest, blessing the forest as I wander. I almost wish I knew a few words of Latin to utter, to add to the image.

I regret destroying the efforts of a spider’s web work. I wish there was a way I could see the webs coming, so I could detour around them, but, unless it is caught in sunlight, the web is essentially invisible to me, as well as to insects. (Interestingly, birds, who can see in the ultraviolet portion of the light spectrum, can see the web and avoid flying through it—to both the bird’s and spider’s advantage. That’s to the bird’s benefit, because I don’t think they can pull out a handkerchief and wipe off the web threads, as I do.) Maybe I could invent an ultraviolet spider-web spotting device that I could don for my walks, to keep me from destroying those hard-earned webs.

Wonderful Web—Part 1

No, this is not a story extolling the virtues of the Internet’s Wide World Web. (Although I have often praised its prodigious offerings of information for my countless researches.) Instead, this posting is about the wonders of the webs that spiders weave. Sitting in the tub the other night, dusk coming quickly on, my eye was attracted by an active blob bouncing around in the nearby trumpet vine. The black blob was barely visible against its dusky background. Being the only thing moving over there, however, it drew my attention.

It took a few minutes for me to realize that the bobbing blob of inkiness was a spider and that it was weaving a web, before bedding down for the night. (Don’t spiders sleep when it’s dark?) I’ve watched spiders construct their amazing webs before, so I could imagine what was happening in the gloom—as it carried on in the deep shadows of the vine, even though I could not see its web at all.

A spider’s web is formed from spider silk—a proteinaceous material made of long chains of very large amino acid molecules. Pound for pound, it’s stronger and more elastic than steel. (That’s why Spider Man can accomplish so many amazing feats with his web.) The spider emits its web filaments from spinnerets on the hind end of its body. (Well, OK, pulling them right out of its ass.) A significant amount of energy is required on the spider’s part to create its silk strands, so it may later eat some of its old web, to recoup that energy, when it comes time to build a new one. Some spiders reel out up to eight different kinds of threads—according to the job each thread is intended to do.

To start its web, a spider feeds out a very fine and sticky thread, which the slightest breeze will swing to and fro, until it contacts and sticks to something solid. Next, the arachnid will delicately rappel down the fine thread, strengthening, tightening, and thickening it as it moves along; turning it into a solid anchor line that will support the remainder of the web. 

After securing a few more anchor lines, the little engineer will then begin adding several radial lines that will further support the spiral web. Most of the spiral threads are very sticky, to trap its meals, as bugs become intercepted by the web. The spider will space several sticky spiral threads with a non-sticky one, upon which to later adroitly run out, to grab its prey.

More web stuff next time…