If you are out and about as summer progresses you might notice the tops of tall grasses and other plants such as nettles wrapped into a ball by spider web. This will probably be the nest of one of our remarkable spiders the Nursery Web Spider. You might even see the long-legged female sat guarding the nest.
Coming in various colours from pale grey to bright orange, nursery web spiders are hunting spiders, they chase prey rather than spinning a web to catch it. Adult spiders mate in late May to June. The male catches an insect and wraps it as a gift for a female. He will approach female to offer the prize and then play dead. If he is lucky, the female will pay attention to the gift and, while she is preoccupied, the male will jump up and mate. If he is unlucky, the female will have him for lunch.
The 150 eggs are laid into a silk pouch about a week later and the female will carry this around in her jaws while the eggs develop. During this time the female will control the temperature for the eggs by basking on top of leaves with the pouch or hiding it under vegetation if the sun is strong.
After about three weeks the female will detect that the eggs have hatched and she will weave a nursery tent among grasses, nettles and other soft plants. The female will sit inside the tent until the young spiderlings emerge from their pouch. Then she moves outside and stands guard. During the day, the young form a tight cluster of spiderlings under their tent but they spread out at night. If the tent is disturbed the defence response is for the cluster to ‘explode’ so there is no great mouthful for a predator. The cluster will reform once the danger has passed.
The young will disperse finally after 4-7 days to begin their independent lives. The adult males die by the end of August, the females may manage a second brood using stored sperm, but they will all be dead before winter sets in.
The young are half-grown as the colder weather sets in and they spend the winter down at grass roots level. In spring they continue hunting and mature into adults ready for the cycle to begin again.
The Nursery Web Spider has one British relative, the Raft Spider, with a body length of up to 23mm and a leg span of up to 7cm, one of the UK’s largest spiders. It lives in bogs and can be seen skating across the ponds on Aylesbeare Common occasionally.
Ed Dolphin
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