St Nicks

Centre for nature and green living

September 2014: Spotlight on … Garden Spiders

Garden Spider - top side

Garden Spider – top side

The Garden Spider Araneus diadematus is probably the best-known member of the spider family, weaving a beautiful circular web and best seen in late summer and autumn. By no means the only abundant urban spider (it has also been found on remote seacliffs from Shetland to Cornwall) it is in our gardens and hedgerows that we encounter its familiar web in its magical splendour.

A large fat spider sitting upside-down in the middle of its web is usually the female of the species, catching insect prey to bring her into breeding condition. The slimmer males also spin webs to attract food to enable them, too, to be ready for the mating season. September is their best month, when hedges, borders, fences, outhouses and car wing mirrors are festooned with their webs.

The web is a wondrous and intricate structure, but what is not often known is that on most days the spider eats its web completely at sundown, thus recycling into its own body the proteins contained in the silk. Then in the night a new web is woven, ready for the coming day’s insect captures. You can see how the Garden Spider weaves its web in these two videos:

http://thekidshouldseethis.com/post/78569540432

http://www.bbc.co.uk/programmes/p00grb0l

The spider’s several spinnerets produce different kinds of silk – some strong like the lines which form the outside framework and anchors of the web, some the tough radial axes into the centre, and some forming the spider’s central sitting area. These are not sticky. Only the main circular web holds the droplets of glue which ensnare the prey. The spider’s feet secrete an oily substance which enables it to walk over the web without getting stuck to it. There is one strong main line which travels through from one side of the web to the other. This is the signal wire on which the spider rests its front pair of feet to sense the vibrations of an arriving trapped insect. When this happens the spider quickly finds the prey, stings and paralyses it, then wraps it in silk to await the meal. Gently touching any part of a spider’s web with a vibrating tuning fork or a modern electronic (not electric) toothbrush usually brings the incumbent speedily to the scene, though after it has been fooled a couple of times the spider quickly learns it is a false alarm.

Garden Spiders: (left) underside (right) male

Garden Spiders: (left) underside (right) male

Autumn’s courtship is a risky business for the male – he approaches the edge of the female’s web and stealthily makes his way across it. As he tweaks her web she can fiercely attack him and occasionally eat him, but he has already prepared a silken escape route and drops down, ready to start again until she signals her submission. He then inserts, with his two palps, silk-wrapped parcels of his sperm into her epigyne before departing in search of another female. Later in the season, now exhausted with the effort, he is more likely to succumb to the female’s appetite for food…. but since his job is finished it means his bodily proteins help to nourish the next generation.

As autumn proceeds the fertilized female leaves her web to find a suitable place to secure her future progeny. In the corner of a window, a crack in a fence, or under a loose piece of bark she lays between 300 and 800 eggs in a yellow silken cocoon. Please don’t disturb or destroy these when you see them – they will grow up to be tomorrow’s garden spiders which capture and eat some of our garden pests.

The female stays by her eggs, guarding them until the first frosts kill her off. The eggs now lie dormant until the following May when the tiny spiderlings emerge in their hundreds, snuggling together in a tight ball. When danger threatens the spiderlings flee on their own infant-woven escape threads to all corners until danger has passed. When the time comes for them finally to separate they release silken threads from their spinnerets which catch the air (it is called ‘ballooning’) and carry the spiderling on the breeze: perhaps a metre or two within the garden, or maybe up in the air and over the fields and far away. Thus the next but one generation begins, for they will not breed that summer but moult several times before overwintering, maturing into breeding condition the year after.

The word spider comes from Old English ‘spithra’, meaning ‘spinner’. The Garden Spider is easily recognized by its plump body, its vertical web and by the cruciform pattern of spots on its abdomen, clearly seen in some of these pictures, all taken at St Nicks.

For further reading: W.S.Bristowe, The World of Spiders, Collins 1958 (Collins New Naturalist series)

19 September 2014 | Categories: Spotlight on..., Wildwatch | Tags: Garden Spider