Sunday, 22 August 2010

More angst for arachnophobes

Although Ruan Pool is pretty well dry, some of the our other pools look suitable enough for waders, yet they're in distinctly short supply so far this autumn. Stithians Reservoir is having a sandpiper-fest, so I can only presume that Simon, the warden up there, is playing dirty and has set up some kind of feeding station for waders. Well Simon, we have a secret weapon that will be kicking in soon and I am strongly tipping Windmill to turn up an American or two before September is out.

So this morning our thoughts turned to butterflies, dragonflies, moths - and spiders again, especially as the overnight mist had left thousands of webs glistening in the sunshine. We found a number of large orb webs very similar to that spun by our resident Wasp Spider (see posts below), but the inhabitants, although quite large and colourful, didn't have quite the same impact as the stunningly scary Argiope bruennichi.

We took a number of photos and were later able to i.d. them as two common species of Araneus, namely quadratus (above) and diadematus (below). Thanks to Dougy Wright for the top left and bottom right photos and supplying his shorts for the backdrop to that at top right.

Tuesday, 10 August 2010

Feeding-time for the beast

I renewed my acquaintance with the Wasp Spider today. The hayfield will be mown soon so I cordoned off the area where it lives. As I approached it I disturbed a grasshopper which jumped straight into its web. Now that's unlucky. It was immediately set upon. They quickly immobilise their prey by wrapping it in silk. It is then bitten and injected with venom and a protein dissolving enzyme. Nice.

This spider is listed in the Cornwall Red Data Book. Rosemary Parslow tells me that they found two in a field on Scilly three years ago. It's amazing how they spread.

Sunday, 8 August 2010

An exciting discovery with a sad twist

I came across the most incredible spider at the farm this morning. The abdomen was about 1.5 cms long and from the tip of the front legs to the tip of the back legs was about 5.5 cms. That is some BIG spider! I was able to identify it from the Collins Field Guide to Spiders as Argiope bruennichi, known as the Wasp Spider. It's a female, full of eggs. That zig-zag ribbon of silk is called the stabilimentum - there are several theories as to its purpose.

In Europe this species is locally distributed in France, Germany and the Low Countries. Following the first British record in 1922, it is apparently now well established in locations near the English south coast and is spreading northwards. The females make their webs in long grass, often near field edges, and that's just where this one was.

An internet search for "Cornwall spiders" led me to, a real enthusiast's resource where you can download a distribution map for every species found in the county. The map for the Wasp Spider shows only seven locations where it has been recorded, the nearest being on the Fal estuary. Coverage throughout the county is patchy but the Lizard and West Penwith have received more attention than most other areas.

I noticed that the maps haven't been updated since April 2006. Another search and I was shocked to learn the reason why. Steve Hopkin was killed in a road accident the following month. He had been a senior lecturer in zoology at Reading University, a scientific associate in entomology at the Natural History Museum in London and was the spider recorder for Cornwall. What is especially poignant is that the biography on his website is still in the present tense. A work in progress was abruptly and tragically terminated.