Nick Baker takes a look at one of his favourite spiders, the purse-web spider
There is nothing like a big spider to get a pulse racing. And while I appreciate this is often for the wrong reason, for me and many other arachnophiles, this group of creatures provides infinite avenues of fascination.
What is the purse-web spider?
The purse-web spider is one of my absolute favourites. While it may not be Britain’s biggest spider, it is certainly one of its more interesting. Found mainly in the south of the country, this nationally scarce spider, Atypus affinis, is a real oddball.
It often surprises folk to learn that we share our islands with a member of the mygalomorphs; a group that also includes the spiders we like to refer to as tarantulas, as well as other much maligned and misunderstood species, such as mouse, funnel-web and trap-door spiders.
Do purse web spiders bite?
Purse-web spiders do not reach the monstrous size of their overseas cousins, but they definitely stand out from the crowd. While they may look like the stuff of nightmares, they are not only completely harmless, it is also highly unlikely that you’ll ever just stumble across one.
Why are they called Purse-web spiders?
Their common name refers to the way that they make a living. They are sedentary, living a solitary life in a silk-lined burrow. The novel design feature of this web-lined tube is that, as well as having a vertical component, it also has an elbow at the top, which runs out over the surface of the ground.
This bit is what you look for when searching for the spiders. However, while it is made of a roughly woven silk, the spider also incorporates bits of debris, such as sand, soil and fragments of vegetation into the weave. The whole affair is a bit like a tatty upside-down sock – even the ‘toe end’ of the web is closed off.
Where do they live?
For the most part, the spider rests in the depths of the burrow, sometimes up to 30cm below the surface. However, if you mimic a landing insect, and try the trick of ‘tickling’ the surface with a piece of grass, vibrations are transferred directly to it through the silk-lined walls of its tunnel. It
can be quite spectacular to see the hollow sickle-like fang tips come tearing through the web, microscopic beads of venom at their tips.
Purse-web spider’s fangs
In fact, the huge fangs make it look all head and no body – the chelicerae can make up nearly a half of the spider’s body length. Watching it move, it has the slow and deliberate gait of other members of this ancient spider group, which has been stalking the planet since the Triassic period, some 350 million years ago. Those attention-grabbing, downward-facing chelicerae are very much part of the story. The way they swing them downwards like a pick-axe is shared with its larger, more exotic, ancestors – modern spiders have their fangs crossing over.
How do purse-web spiders mate?
It can take over four years for purse-web spiders to mature. And, around October each year, a cohort of ‘new’ males will leave their burrows to go in search of a female. While they are solitary for the most part, they do live in colonies, so males don’t have to walk too nfar to find a partner.
When they do stumble upon a purse web with a receptive female in residence, a male will tear their way in and mate. They’ll live together for a while but, eventually the male will die or become dinner. The eggs hatch the following year.
Illustration by Peter David Scott/The Art Agency