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Field Notes

Covering the natural wonders of the Pacific Northwest

April 18, 2013 at 11:48 AM

The mystery spider is revealed

Our mystery spider was Dysdera crocata (Matt Ironside / The Seattle Times)

Our mystery spider was Dysdera crocata (Matt Ironside / The Seattle Times)

In my last post I challenged people to identify this unusual red-fronted spider, and many readers were familiar with it.

According to Rod Crawford, the curator of arachnids at the Burke Museum, this spider is likely Dysdera crocata. It goes by one of several common names all related to its main source of prey, the woodlouse. If you’re not familiar with woodlice, you probably are by another name, pillbug, sowbug, potato bug, and armadillo bug just to name a few.

The woodlouse spider is relatively new to our area and appears to be moving north from Oregon as our local climate warms. The species is native to Europe and was introduced to North America sometime in the 19th century.

It made its way west to Portland by the 1930s but has been slower to move north. It didn’t cross the river into Vancouver until the 1980s. According to Crawford, the time it took to move north is pretty good evidence that its spread was being limited by climate.

Beyond the wagon-red color, which immediately called the spider to my attention, I noticed its long nasty chelicerae, which is a term I must admit I just learned. Before I would have called them “fangy things.”

Pillbugs are the main prey for Dysdera crocata. (Matt Ironside/ )

Pillbugs are the main prey for Dysdera crocata. (Matt Ironside/ The Seattle Times)

Those fangs appear to have given the woodlouse spider a reputation for being venomous that it doesn’t really deserve. They are long and strong to puncture the exoskeleton of its main prey, but apparently the strength of bite is where the nastiness ends as far as humans are concerned. If you want to read more about it, see a clearer picture of Dysdera crocata and read about spider danger myths, Crawford has a good page devoted to it.

Crawford’s whole site on debunking spider myths is a very good source on local spider information.

I’d also like to congratulate Christina Wilsdon, who was the first Times reader to correctly identify our mystery spider.  If you have a good photo of some interesting biota from our area, send it our way and it might end up here in Field Notes.

0 Comments | Topics: identification, spider, woodlouse spider

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