Friday, 6 May 2011

Its a date with Dolomedes fimbriatus

Yesterday I had a hot date with a rare and exotic female, no not Catherine Duchess of Cambridge, but the beautiful raft spider, Dolomedes fimbriatus.

We travelled up to the Shropshire Mosses and Meres to see this beauty. There are two raft spiders in the UK, the very rare Fen Raft Spider, Dolomedes plantarius which is only found at a handful of sites in East Anglia and the South East and the widespread but very localised in distribution raft spider. Bizarrely the rarer of these two is quite well studied, however the ecology of fimbriatus is hardly understood at all. And they're not easy to find either in boggy landscapes, unless that is the big females are on water. And when I say big, I mean big.... they'd give the canny lasses in Newcassel on a Friday night a run for their money. Yep that big.

But before I allow you to see this big lady, let's have a crafty peek at the weedy, pale wimpish male raft spider above. There were quite a few scuttling about in their meek lily livered way, but even these had a style of their own, so well camouflaged too. But then we found a female, well camouflaged too but absolutely stunning.........

These are just stunning arachnids. And yes the female is huge, the biggest spider in Europe. The one below was about 7-8cm long from leg tip to opposite leg tip, the body about 3cm.

These photographs don't do this spider justice as the body was like chocolate brown velvet with a lemon curd go-faster stripe down each lateral side. As hunting spiders they spend a lot of time waiting for prey on water, using water tension to support their weight. However they are attached to a piece of vegetation using their hind legs and a tiny thread of silk.

One curious piece of this species ecology is that if a male approaches to breed and she thinks, nahh far too weedy, she just eats him. Not after mating as many spiders do, but before mating. Now that does have a slight ecological problem in that if the last female was on the planet, would she eat all the males and become extinct?

I'm glad we found some spiders as with this very dry spring we're currently experiencing the Moss we were visiting was almost dry. The two females we found were actually in puddles around an ancient tree stump, this was the only open water we found. We need rain, and lots of it soon.

If you want to find out more about these fascinating beasties, I'd recomment the Dolomedes website http://www.dolomedes.org.uk/


  1. I feel a linocut design brewing!

    I love your description "chocolate brown velvet with a lemon curd go-faster stripe".

    And it just goes to show you don't mess with a fen girl!


  2. Now that is a spider. An absolutely gorgeous photo on your header.

  3. Hi Celia, Funnily enough this morning I'm off to the art shop to get some linocut odds and ends, as I was impressed by your hare a while back. I shall experiment. If you'd like the original photos to work from, drop me an e-mail.

    Hi Lisa, they are stunning spiders, very serene, but intimidating at the same time.

  4. Oh my, I can't get my head around the size of the old girl. Great information you've given as well. I must say I laughed out loud when I read that she eats the male if it's too weedy. (naughty of me I know.) The picture on your header is fantastic!

  5. Hmmmmm, I think I will not look at this post too closely...me and spiders don't get on.
    There is a house spider living in the speaker of the stereo we use at work and now I can't go near it....which is a problem on night shift if I can't switch it off!....I do love all other wildlife :-0

  6. Now Goosey :-) I think the most ardent arachnophobe would come to love these serene beauties. If you don't believe me, maybe listen to Living world, Radio 4 06.35 on May 22.... or of course the i-player.