The Atavism

Sunday, May 1, 2011

Sunday Spinelessness - All in the eyes

Can you guess what these patterns represent?

Well, having read the title of the post you may have guessed that each black dot is an eye. In fact, these pictures all represent the way a particular family of spiders arrange their eyes. For spiders, the eyes are a window into evolutionary history: the ancestor from which all spider species descent had eight eyes, and, although most modern spiders have kept all eight, they arrange them in an astounding number of patterns. Very often, the eyes are the best way of placing an unidentified spider into at family. (These pictures are from Lynette Schimming's article on BugGuide, they represent the families Ctenizidae (trapdoor spiders), Oxyopidae (lynx spiders) and Scytodidae (spitting spiders) and are Creative Commons by-nd-nc licensed).

So, when I found this spider lurking under a log, and couldn't place it into my (admittedly scant) knowledge of spider taxonomy I was very keen to get at least one photo of its eyes (as it turned out, it was also by far the best photo I took of this spider before turning its log back over):

There are a couple of families of relatively large ground dwelling spiders in New Zealand, and and first glance I thought this might be a vagrant spider but the eyes are just all wrong for that placement. I had to dig a little deeper for the answer, but between google and Flickr I found it. You are looking at a member of the family Cycloctenidae.
The drive many naturalists have to call each thing by its right name might seem oddly obsessive, but learning a creature's place in nature isn't the same as placing a stamp in the right section of an album. A taxonomic name can be a key to data collected by hundreds of people. In this case, Ray and Lyn Forster wrote about the Cycloctenidae in Spiders of New Zealand. It seems the family is restricted to New Zealand and Australia and has only a few known genera. They are commonly called "scuttlng spiders" because the arrangement of their legs allows them to run sideways as well as forwards and backwards, which means than can rapidly hide from a would-be predator. That's no-doubt a predator avoiding adaptation, but this particular spider was very happy for me to rest a camera directly in front of and get the shot that let me know what I was looking at.

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Posted by David Winter 7:32 PM

1 Comments:

Great comment about the naturalist drive to identify their subjects.

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