Linyphia marginata

I first met Linyphia last Sunday – the same day I watched Venus slowly drowning in the dawn sky. I had gone for a mid-morning walk down along Laurel Ridge. Dew lingered in the cool woods, and the sun was at just the right angle to give the impression of one, virtually continuous wood-wide web.

Less than a hundred yards from the house I stopped for a while to watch a spiny micrathena – our most common forest-dwelling Epeiridium spider – working on a new web in the tops of the laurel bushes, right at eye level. Two other cobwebs hung right behind her, at 30-degree angles from the one she was building. As many times as I have watched this process, it’s always spell-binding to see how smoothly the legs of an orb-weaving spider can navigate the radiating lines, how quickly the abdomen dips to attach the unwinding spiral at each intersection. It’s not so much weaving as it is a form of knitting, I think. And of course this species, with its odd, hobnail-shaped abdomen, makes for an especially intriguing spectacle.

Since I was walking in an easterly direction, it was easy to become entranced by the prismatic effects of a forest full of silk. Long strands dangled down from the treetops like unbaited lines of celestial fishermen: these were, of course, caterpillars’ rappel lines. The white, bristle-brushy tussock moth caterpillars are especially numerous this year, but dozens if not hundreds of other species are also at the larval stage right now. Otherwise, the upper layers of the forest seemed dominated by various species of orb-weavers (Epeiridae) and mesh-weavers (my name for the family Therididae, makers of most of the loose and irregular webs one sees, including those in the upper corners of rooms). The first two or three feet above the ground were dominated by various species of Agalenidae, which I tend to refer to either as tunnel spiders or handkerchief spiders – the latter especially after a heavy dew, when Agalenid webs can turn a lawn or recently harvested field white.

It’s a shame that most spiders don’t have common names. In my own idiolect, tunnel spiders are those common, forest-dwelling spiders that weave dense, flattish webs and hide in tubes or tunnels. Agalena navia is the most common species, which “varies greatly in size and color,” according to James Emerton’s Common Spiders of the United States (Dover, 1961 [1902]). I can attest to that! During my niece Eva’s visit last May, we discovered the joys of dropping ants onto A. navia webs and waiting for the spider to rush out of its hiding place, the tunnel itself often hidden strategically under a dead leaf. It was easy to assume we were looking at different species: “Large females may be three-quarters of an inch long, with legs measuring an inch and a quarter, while others may be full grown at half that size. In color some are pale yellow with gray markings, and others reddish brown with the markings almost black,” says Emerton. Whatever the case, they move so quickly that what one mostly sees is a small, hairy blur dancing around its prey, lasso twirling.

On last Sunday’s walk I became aware of a different kind of web, less common but occupying the same, bottommost layer of vegetation (chiefly blueberry and huckleberry bushes). The first one I noticed took my breath away: a spherical cluster of shifting points of prismatic light, like a tiny alien space craft hovering a foot above the ground. I stood for a while leaning against a tree and watching it from about six feet away. When the sun moved off it, it became almost invisible. I got down on my belly and inched forward.

As I got closer, I realized that the web was not spherical but bell-shaped, with a depth and width of about six inches each. A thin haze of additional threads extended for a few inches above the apex of the bell or dome. When I got within a foot away, its occupant – a small, thin-bodied spider with light yellow legs and a striped abdomen – darted down the side, but when I retreated she quickly returned to her station inside the top of the bell. The weaving was somewhere between the Theridiae and Agalenidae in denseness.

This was my first encounter with Linyphia marginata, of the Linyphiad family. It’s a common enough spider, apparently; I had overlooked it all these years in part because of my bad habit of daydreaming, and in part because, as Emerton notes, it uses exceptionally fine threads, building a web “so transparent that it easily escapes notice unless the sun shines upon it.” With the sun at just the right angle, I found three more in the next ten minutes.

How wonderful, I thought, that the woods could be so full of gossamer bells and I could fail to notice! And how humbling. I figured that the unique shape must be designed to catch small insects such as gnats and winged ants as they took flight from the forest floor, but Emerton claimed the opposite:

The spider stands all the time under the top of the dome. Insects flying near touch the threads above the dome and, their flight being broken, drop down among closer threads and, finally, to the dome itself, where they are caught by the spider and taken through the meshes. Remains of insects and other rubbish are cut loose from the web and dropped. The webs seem to be used for a long time, but if they are injured a new one is soon made, either in the night or day, and the remains of several old webs are often seen hanging flat and torn beneath a new one. The dome is begun at the top and extended downward by inclined threads, an inch or two long, which are crossed by shorter threads in all directions. The spider works very rapidly, but I have never seen a dome finished, the spider always working for a few minutes and then resting a long time.

So the unique shape is designed for the convenience of the spider, enabling it to race to any point of the web at top speed. Whereas an orb weaver like the spiny micrathena relies on the stickiness of its silk to hold the prey until it can get to it, L. marginata gambles on an insect’s physical entanglement in the labyrinthine meshwork of short, fine lines. Since discovering this lightning-swift spider that sits upside-down all summer under a bell of such striking design, I wonder if I will ever again be so entranced by a glinting web of a mere Empeiridium?

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Dave Bonta (bio) crowd-sources his problems by following his gut, which he shares with 100 trillion of his closest microbial friends — a close-knit, symbiotic community comprising several thousand species of bacteria, fungi, and protozoa. In a similarly collaborative fashion, all of Dave’s writing is available for reuse and creative remix under a Creative Commons Attribution-ShareAlike 3.0 United States License. For attribution in printed material, his name (Dave Bonta) will suffice, but for web use, please link back to the original. Contact him for permission to waive the “share alike” provision (e.g. for use in a conventionally copyrighted work).

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