Monday, 15 September 2008

Garden Spiders

This is an illustrated account of the life cycle of the common garden spiders, Araneus diadematus, one of the most obvious invertebrate species in the September garden. The spiders have spent all summer growing and the females, now full of eggs are very large.
The spiders are born out of their silky cocoon in May and form striking spiderling balls, where all newborn spiderlings stay together in a tight 'ball'. If they are disturbed, they disperse in different directions a short distance, but regroup again shortly afterwards.

Eventually the tiny spiderlings, yellow with a triangular black mark in the abdomen, disperse and make miniature versions of their orb-web amongst the vegetation.

Males are usually darker than females and have small abdomens, whereas females have globular abdomens. Both have white marks in the shape of a cross on their abdomen. Tone can vary quite a lot, there are darker and paler individuals.

I have seen garden spiders trap and subdue a range of invertebrates, usually flying insects, from aphids to lacewings, to Eristalis flies and wasps, even butterflies. Bumblebees are strong enough to break free though.

As I have mentioned in other post, I have been lucky enough to watch the garden spider courtship in the comfort of my own home (male on the left) . The whole business took some time, and despite his apparent care, the male ended up as food for his mate (right). I don't think he managed to mate, the only contact we observed was between the front legs.

In the autumn, the female makes a silk cocoon and lays her eggs there, which is the usual overwintering stage. Here is a photo of a female who laid her eggs in a corner of the outside toilet. She stayed with the cocoon until she dissapeared (presume dead, but I never saw a body).
Something that surprises me is the range of sizes of spiders that are found in September. The larger ones surely will lay their eggs before winter arrives, but I doubt the smaller ones will. Maybe there is some overwintering of adult females in sheltered spots? I found this large specimen near the house in March.

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