Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Sunday, March 05, 2006

Huntsman Spiders.

Anni has published a comment on the latest David Attenborough series of TV programs, called "Life in the Undergrowth". Specifically she wrote about Episode 3: "The Silk Spinners", about spiders. Anni, being Anni, of course, wrote about the music in the program, as much as its visual content. But she acknowledged that the photography and the research was fantastic. I agree with her on that point. Of course, my only comment on the music was that I was oblivious of it, which for me, means it was a successful sound track. But I shall listen for the music tonight. (Sunday. ABC TV 7:30 pm)

She illustrated her comment with a nice photo of a Huntsman Spider inside her house, with a hand in frame, as a nice scale reference. Anni was debating whether Huntsmen Spiders use webs to catch their prey? She did not think so. I can assure her that they do not. They are stalkers of their prey, with excellent eye sight, and great agility.

Robertson residents all have "pet" huntsmen around the place - it goes with the territory. Rather, we are within their territory. My daughter Zoe, who has just moved to Robertson, has not yet learnt this fact, but I'm giving her time to adjust.

Anyway, while not wanting to compete with Anni's nice photo of a Huntsman Spider, I thought I might complement her "clean" photo with a "messy action shot". This large Huntsman (Genus: Isopeda or Isopedella) was on the outside of my kitchen window last year, and it had just caught and devoured a Hawk Moth (Family: Sphingidae)

Moths have fine scales covering virtually all their wings and their bodies, and clearly, from the "dust" all over the window, in this photo, there had been a very heavy struggle. The "dust" on the glass is from the moth's scales, shed as it fought off the spider, unsuccessfully. The particular Hawk Moths which were around Robertson, back in November, when I took this photo, have a rusty red colour to them, the colour of the "dust" on the window.

From the marks on the window, I was able to measure this spider (after it had left) for it did not like me photographing it this closely, as being 3.5 cm long (in the body) and 11 cm across in the legs. As a matter of interest, there is the faint reflection of an upside down "bottlebrush" (the cleaning implement, not the flower) in the window, which might help give you a scale reference.
For the record, I have since cleaned the window.

Consider this, though, not only can a Huntsman Spider walk over a vertical sheet of glass, it can trap a moth (from the markings on the window, a large moth) and kill it there on the pane of glass, without losing its grip.
How successful is that, as a hunting technique? An appropriate name for a hunting spider, eh? They are stalkers of their prey, and have excellent eye sight, and great agility.

The web page linked here suggests that spiders with the ability to climb on extremely smooth surfaces, such as on glass, (and not all have that ability) can do so because of their extremely fine hairs on their legs which can adhere to the faintest trace of water on that smooth surface (scroll down to the 60 power magnigfication photo of a spider's leg, on that website). Basically, they are using the surface tension of the film of water on which to walk. At night, in Robertson, just about any window pane will have a film of moisture on it. So that explanation makes sense to me.

It is refreshing to write about the creepy-crawly parts of the Nature of Robertson, rather than its politics, for once. I thank Anni for the inspiration to do that.