Dear Readers, some of my favourite toilet-side reading is the journal of the British Arachnological Society – it had that wonderful story about the lady who rescued spiders that fell into her swimming pool, and this month it has introduced me to the concept of the Garden Centre Spider (Uloborus plumipes). As you might expect from the name, this rather dashing little critter lives in heated greenhouses and yes, garden centres – it originates in Africa and southern Europe and so it finds our winters rather too cold for its liking. It’s thought to perform a role in hunting down and gobbling up whitefly, which is a very good thing if you’re growing, say, orchids, and came to the UK originally from the Netherlands, probably in a potted plant.
The species name ‘plumipes’ means ‘feather-footed’, and if you look closely at the photo above you can see that there are ‘hairs’ on the ‘front legs’. But the subject of the article in my magazine was not so much the little spider itself (and it is little, maxing out at about 6mm long). The web is usually horizontal, and is unusual because the spider has an organ called a cribellum, which enables them to comb the silk into fluffy, fuzzy threads that can catch prey without the need for stickiness. Furthermore, the spider dangles underneath the web, and the whole impression is of a web long neglected and dusty, a perfect lure for some unsuspecting insect.
The article was particularly interested in structures in the web known as stabilimenta – these are areas of dense, opaque silk that, in spite of the name, are not thought to add to the stability of the web. I’ve seen these ‘designs’ in the webs of tropical spiders, and I wondered if they served to make the spider look bigger and protect it from predators, though this would probably make the web and the spider more visible. Another theory is that these patterns serve to make the web more visible to birds who would otherwise fly through them and destroy them. Whatever the reason, the Garden Centre Spider often makes them, and the author of the piece, Geoff Oxford, was interested in whether there were more or less stabilimenta in wild spiders (the data on these was from a similar but not identical species) as opposed to garden centre populations, and if so, were they different in design? Well, after many hours of standing in Dean’s Garden Centre near York with binoculars raised (the spiders tended to build their webs in the most inaccessible corners), Oxford came to the conclusion that the ‘indoor’ spiders built far fewer webs with these features than wild spiders did. Furthermore, while the ‘indoor’ spiders built lots of linear structures, like the one in the photo below, they were much less likely to build circular ones (see Argiope spider in second photo below) than their wild cousins.
One thing to bear in mind is that the ‘cost’ of producing these structures is very expensive to the spider, so it must be worth their while. Maybe there’s an advantage if you’re living ‘in the wild’ where you stand more chance of being predated or having your web damaged? And if you’re living in a comfy, centrally heated garden centre, with whitefly on tap and only an occasional trapped robin to contend with, you don’t need to bother?
The questions raised beg for someone else to go and stand in their local garden centre with binoculars raised, while ‘normal’ folk edge past with gritted teeth. That could be me, readers! It’s all very intriguing. I can (almost) feel another post-retirement project coming on.