Sunday, May 8, 2016

7-May-2016 Snoqualmie, Washington

Sample site location. Click to enlarge.
Since finding the introduced crab spider Ozyptila praticola (Thomisidae) in Snohomish last week, I've been eager to continue my search for it eastward up Route 2, which follows the a river valley into the Cascades.  But I learned years ago that Route 2 on beautiful weekends like this one is a traffic headache to be avoided, so it'll have to wait until a weekday.  So today I continued the eastward search further south, along Interstate 90.  My destinations: Snoqualmie and North Bend.

Trees on the right were the cone source
View between the rows
I knew when I spotted the long, double row of Douglas-firs (Pseudotsuga menziesii) growing beside Snoqualmie Elementary School that if O. praticola were present in the area, I'd have a good chance of finding some here.  Groundskeepers had allowed the trees' fallen cones and other tree litter to accumulate, the cones appeared untrampled, and the cone scales were well opened.

The fallen cone microhabitat
Both male and female Ozyptila
were present
Enjoying the dense shade provided by these trees, I tapped 50 cones and collected 15 spiders from 4 families and at least 3 species.  The most numerous spider present was none other than O. praticola.  This finding puts the eastern edge of its known local range in the foothills of the Cascades (see map above).  The other mature spiders I collected remain to be identified but included a female Clubiona (Clubionidae) and some linyphiids.  The sample also contained 34 juvenile and 1 adult harvestmen.  This was a busy set of cones!

Having found O. praticola in Snoqualmie, I decided to drive further east into the Cascades for another sample.  I found numerous Pinus nigra trees planted around a gas station about 6 miles further into the mountains and tapped 100 of their fallen cones.  Sadly, upon returning home, I discovered that I had lost the sample vial!  The sample did contain numerous crab spiders, which appeared to me at the time of collection to be Xysticus rather than Ozyptila.  But of course the juveniles present in the sample were too small for me to distinguish.  I'll have to re-sample the area at another time. UPDATE [Aug 2017]: I eventually found the lost vial! The crab spiders in the sample turned out to be Bassaniana utahensis (Thomisidae) and Apollophanes margareta (Philodromidae). There were no O. praticola present.

Mount Si as seen from Snoqualmie-North Bend Road

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