Saturday, January 21, 2012

The Spider who was Determined to be on the Web.























There's quite a varied spider fauna on the window ledge in the room where I work (examples here and here) and this very small zebra spider put in an appearance at the beginning of the week, exploring my desk and even my computer keyboard. Since it seemed so eager to get itself on the web, I thought I'd oblige. The pictures are not very good because it really is tiny - just a few millimetres long - and these are small sections of the whole frame.























Zebra spiders don't actually spin a web to capture their prey. Instead they stalk it then leap onto it from a distance. They can do this with remarkable accuracy, thanks to the two large forward facing eyes that are somewhat akin to a pair of binoculars.


There are two further pairs of smaller eyes on either side of the central pair, so this arachnid has almost 360 degree vision. I find it hard to imagine how its relatively simple brain can process, prioritise and respond to all that visual information. It must be like watching six TV screens at once.


As you can see from this angle, its difficult to creep up on a zebra spider from behind - there's a rearward facing eye watching both flanks.

Although zebra spiders don't spin a capture web they do anchor themselves with a thread of silk, ready for instant escape ....... which is what my specimen did when I got too close with the camera ..... it bungee-jumped from the window ledge then climbed back up its escape thread when it thought the coast was clear. The other role of this escape thread is as an emergency safety line, in case the fly that it leaps on carries it aloft before the spider can subdue its victim.

9 comments:

  1. Fascinating! Quite the internet debut.

    ReplyDelete
  2. A grand post. I'll keep two eyes out for these.

    ReplyDelete
    Replies
    1. I associate zebra spiders with warm summer days so I was really surprised to see this one, in the depths of winter, Adrian...

      Delete
  3. An amazing little creature Phil.

    I've not seen one of these in ages. I used to see loads when I was a kid, scurrying around.

    ReplyDelete
    Replies
    1. I always associate them with childhood too Keith - there always used to be at least one sunbathing on the window sil on the outside of out house, waiting for an unwary fly to land...

      Delete
  4. Brilliant! Two masters in their field in the same blogpost.

    ReplyDelete
    Replies
    1. Wish I had eyes in the back of my head too..........

      Delete