Nature’s drapes of spun lace
Suspended in fields and hedgerows, the lacy artwork of the spider’s web is an ethereal but effective trap
In the stillness of an early October morning, a lilac bush appears to glisten in the first rays of sunshine. Strung between its branches is a delicate spider’s web, its filmy threads covered in droplets of dew that sparkle in the light. Elegant circles of silk spiral between a wheel of filaments that radiate from its centre, in a form of ephemeral beauty. At the heart of this creation sits the architect of this stunning piece of natural engineering: a garden spider, waiting for her prey. It has taken the spider a mere 20 minutes to spin her web, a task she performs anew each morning. She builds it using only the sense of touch, her long, sensitive legs drawing out silk through a series of tubules, called spinnerets, on the tip of her abdomen. In it, she catches the mosquitoes, greenfly and other insects on which she feeds. Although both male and female garden spiders spin webs from birth, the male stops doing so when he reaches sexual maturity, at approximately eight weeks. “Garden spiders are responsible for most of the orb webs that we see in our gardens. These are the round webs people typically think of as spider webs,” says Lawrence Bee, of the British Arachnological Society. “The name is actually a bit misleading, as garden spiders are found in many places, such as woods, heaths and clifftops; anywhere, in fact, where there are trees or grasses from which they can hang their webs.”
Garden spiders are just one of between 30-40 species in Britain that spin elaborate and intricate orb webs. But there are other types of web, perhaps not as elegant, but just as effective in trapping insects. The simplest form is a tube web. These are built by spiders, such as the tube spider, in rock crevices or holes in walls. They line these fissures with silk before spinning trip wires that radiate out around the mouth of the opening. The spider sits inside with a leg on each trip wire, alerted to vibrations from passing prey. Tangle webs, so called because they are a mass of tangled up silk threads, are spun by spiders including the cellar spider and daddy long legs spider. Hidden among the mesh of silk are taut trip wire threads stuck to an attachment point with a drop of glue-type gel. The struggles of any insect that gets stuck in the glue will break the trip thread. As it springs up, it pulls the insect into the net-like web. Sheet webs, spun by the familiar money spider and common house spider, work in a similar way. This time, a thin sheet of silk is strung between two walls or blades of grass, with taut lines of thread stretching above the web. Should an insect collide with these threads, it is knocked down into the sheet below. Lace webs are made of a very fine ‘woolly’, blue-grey silk, which the spider
“The bird a nest, the spider a web, man friendship” William Blake, ‘The Marriage of Heaven and Hell’
‘backcombs’ with a leg as it emerges from the spinneret. The minuscule hooks formed snag any insects that land on the web. These webs are often spun in the corners of windows and under flowerpots, by the window lace-weaver spider.
The silk produced by spiders is finer than a human hair, but weight for weight is stronger than steel. It is also incredibly resilient and elastic, able to stretch up to four times its length without breaking. Largely made up of two proteins, fibroin and sericin, it is produced as a liquid in glands in the abdomen. These are attached to the spinnerets that open onto the surface. As the liquid silk travels through the spinnerets, it solidifies into a thread, the thickness of which is controlled by a valve which can widen or narrow. All male spiders produce at least three types of silk, and females four. “Spiders use silk in lots of different ways, and some can produce as many as seven different types,” says Lawrence. “Dragline silk, the long strands you often see spiders hanging from, is particularly strong and elastic, and acts as a safety rope, allowing spiders to investigate their surroundings or to make a quick getaway. Silk is also used to wrap up prey, and females produce a special type which they use to make an egg case. Young spiders use very fine gossamer silk in dispersal. And, of course, silk is used to spin a web, which itself will contain more than one kind of silk.”
Garden spiders usually build their webs between 3-6½ft (1-2m) from the ground, strung between a framework of dragline-strength flexible silk. They follow the same pattern for every web they spin. “Each morning, the female spider will climb to a high point, the top of a bush or a fence post, and release a thread of silk,” he explains. “This will drift in the breeze, eventually catching on something; another bush, perhaps. The spider will sense this, pull on the line to tighten it and then walk along it. As she goes, she reinforces it with a second strand to create a strong bridge.” The first stage of building work complete, the spider now spins another thread of silk below the bridge line and attaches it at both ends. “The centre point of this line will become the centre of the new web,” says Lawrence. “She goes to this point and then drops down on a line of thread, pulling the upper line down to create a ‘Y’ shape. These three lines, all made of dragline silk, form the first three radial threads of the web. Their ends are attached to framework threads that she has positioned around the sides, joined to the anchoring bush or post.” One by one, more radial threads are added. They are evenly spaced, the gap between them never so wide that the spider cannot cross it. As a result, a spider’s web is always in proportion to the size of
the spider making it, and webs are biggest in autumn when spiders are fully grown. “Radial threads complete, the spider goes back to the centre and spins a spiral of finer silk between them, from the centre out,” he explains. “This is actually only a temporary structure, and the spider uses it to walk on during construction. Having reached the outside of the web, she then turns round and goes back the other way. This time, she spins a permanent spiral, with the loops closer together, eating the temporary one as she goes. As she lays down the new silk, she secretes drops of glue and twangs each thread with her leg. The droplets scatter down the threads, creating a sticky surface that will trap her unfortunate prey.”
Once the web is complete, the spider will usually position herself on a platform of criss-crossed silk threads she builds in the centre, hanging upside down from the underside of the web. She will know if prey has been snared. “Her legs are so sensitive that she can pick up tiny vibrations,” explains Lawrence. “Anything struggling will get her attention, and she will move across the web towards it. A seed or something static that might have been blown into the web will be ignored. Having three claws and special brush-like hairs on the end of her legs, she doesn’t stick to the web herself.” When she reaches her quarry, the spider pierces it with her fangs and injects venom from a gland under the jaw. The insect is immobilised and dies in seconds. As more insects hit the web, along with pollen, dust and other debris, it can lose its stickiness. It may also be damaged in strong winds. To make sure she does not go hungry, the spider will spin a new web every morning, eating the old one to recycle the silk proteins.
As spiders grow, they must shed their skins as their rigid exoskeleton cannot grow with them. Moulting is very strenuous, and the spider may even die during the process. Hanging from a thread of dragline silk, the spider increases its heart rate so much that the rise in blood pressure causes the outer covering of the head and thorax to lift. The sides of the abdomen then part, and the spider gradually wriggles its way out of its skin. It may take hundreds of twists and turns to do this, legs often proving a particular problem. Once free, its tissues expand to their new size and the exoskeleton hardens once more. The old skin, called the exuvium, dangling on its line of silk, may easily be mistaken for a dead spider.
The next generation
The reproduction process of a spider begins when an eight-week-old male wanders in search of a female. When he finds a web with a likely partner, the male plucks and vibrates the threads in a special rhythm so that he is not mistaken for prey. Gradually, he edges towards the female. If she is receptive, mating takes place, usually in mid summer. The male spins a small web on which he deposits sperm. He then absorbs the sperm into his two sensory organs, called pedipalps, and places them in the
“A big bud of moon hangs out of the twilight, Star-spiders spinning their thread Hang high suspended, withouten respite Watching us overhead.” D H Lawrence, ‘Liaison’
female. He dies soon after mating. As winter approaches, the pregnant female lays as many as 100 eggs, which she wraps in a protective silk cocoon. Initially, she may stand guard over her eggs, but, weakened by the birthing process, she will die before they hatch the following May. “If you look carefully in the garden in spring, you may see a mass of tiny spiders surrounded by a cloud of threads,” says Lawrence. “This is the remains of their cocoon, and if you prod the threads, countless spiderlings will run out, scatter, and then shoot back together again. It’s fascinating to watch.” After a couple of days, the spiderlings begin to seek new horizons. They climb upwards, scaling a stone or a blade of grass, and release a tiny strand of gossamer silk. Ready to spin webs so small they are practically invisible to the human eye, they float away on the breeze, and the cycle begins once more.
Having created a wheel of radial threads, the spider links them with a spiral of finer spun silk, starting from the centre of the web and circling outwards.
A grassy field draped with sheet webs, which dip like hammocks, ready to catch the spider’s prey.
Delicate lace webs are often found in the corner of old windows and have a bluish tinge.
A tube web around the opening of a hole in a wall with threads spreading out from the entrance to catch out insects.
Like yarn pulled taut between spools, sheets of web catch the early autumn light.
Morning dew settles on a tangle web, enveloping plants in a mesh of tangled threads.
After climbing to the top of stems on which to attach her web, the female spider creates a net-like curtain between them.
Rising water levels force spiders to retreat to higher plants, covering them in a silken canopy of thread.
Droplets hang from fine threads like strings of glittering beads adorning the leaves.
Lawrence Bee is lead author of Britain’s Spiders: A Field Guide, and committee member of the British Arachnological Society.