Category Archives: spiders of Britain

Fen Raft Spider breeding project

Spider expert Helen Smith has been raising thousands of Fen Raft Spiders in her kitchen, feeding them flies in their test tube nurseries.  But now the surrogate mother has broken the bond and the spiderlings have to go it alone, after being set free in a Suffolk nature reserve.  The Fen Raft spider is a seriously endangered species, one of only two protected spiders in Britain, living in isolated enclaves.  The parents of this new generation of spiderlings were picked from separate populations to enhance their genetic diversity.

Mothercare spiders

The Mothercare spider (Theridion sisyphium), common in the UK and continental Europe, has earned its name by the way the females look after their young.

Very small and strikingly marked, Mothercare spiders often pitch their webs in thistles and gorse, whose spines offer a defence against predators, as well as being useful for anchoring the web. The contrasting brown/black and white patterns on the abdomen turn out to be an effective camouflage, as they break up the shape of the spider.

Within the web, the female spider builds a dense silk retreat among leaves and leftovers of eaten insects. Here the spiderlings will hatch from a blue-green egg-sac. In their first days they are fed by their mother, who regurgitates digested food into their mouths, behaviour we associate with birds. Continue reading Mothercare spiders

Wasp spiders in Britain

Wasp spiders ( Argiope bruennichi) are originally from Continental Europe andeprobably arrived in Britain from a Channel port in the 1920s. Since then they have been gradually spreading their domain across the south of England, reaching Cornwall and encircling London. The amorous practices of these spiders are interesting. The male waits on the threshold of the female’s web until she has shed her skin to become mature. He then takes advantage of the fact that the female’s jaws are soft to mate with her in safety. Many males, however, in their impatience misjudge things and are eaten while engaged in the act. Note, despite its threatening colouration this is not a dangerous species. The wasp-like appearance is probably to deter predators. In the very unlikely event of a bite the effects are likely to be mild swelling and itching at the site of the bite.

The Raft Spider – Britain’s largest spider

In fact two spiders qualify for this title, but they are so similar that only experts can tell them apart: Dolomedes plantarius and Dolomedes frimbiatus – the Raft Spiders. The females can span an impressive 7 cm, from leg-tip to leg-tip, with a body of up to 22mm. The males, as usual in spiders, are notably smaller, with a body of 10 -13mm.

Chocolate brown, with creamy white stripes, Raft Spiders live in watery habitats, typically fens and marshes.  They are found at the water’s edge, resting their legs on the surface. Vibrations in surface tension inform them about what’s happening in their vicinity. Continue reading The Raft Spider – Britain’s largest spider

The most venomous spider in Britain

This title has been awarded to an invasive species, Steatoda nobilis, known as the Biting Spider or False Black Widow.  It first arrived in England around 1870 on a shipment of bananas from the Canary islands to Torquay. Its bite is likened to that of a Continue reading The most venomous spider in Britain