How widespread is Ozyptila praticola in Washington state?

Ozyptila praticola collection sites in Washington

In 1953 Willis Gertsch reported that a male Ozyptila praticola (Thomisidae) had been collected at an unspecified location in Seattle, Washington the previous summer.  Of this discovery Gertsch wrote, "This is the first record of a Palearctic Ozyptila from North America. The single male agrees in detail with specimens from Finland. Whether the species is established in Washington or is a casual introduction must still be ascertained."

Since then, Rod Crawford and others, including myself (here and here), have collected the species from several localities in northern Seattle (red pins, right).  So the species appears to be well established in the city, but how widely it has disbursed into the state, assuming that Seattle was the point of introduction, is still an open question.  It was found in several locations near Vancouver, British Columbia in 2009 (Bennett et al., 2014), but its present status there is unknown.

To get a clearer picture of O. praticola's local distribution, I've started tapping pine cones both to the north and to the south of the spider's known locations in Seattle.  What follows are descriptions of my first two such forays (see green pins on map).

24-Sept-2015 Beer Sheva Park, Seattle, Washington

Beer Sheva Park cone site

Fallen cones on needle litter

Beer Sheva Park is a typical urban park with small groves of conifers bordered by lawn and pavement.  I tapped Pinus nigra cones found on the lawn as well as those resting on needle litter.

Tapping 100 cones I collected 30 spiders and 12 harvestmen.  Ozyptila praticola was the only identifiable species in the sample and was represented by 1 female, 1 male and 15 juveniles.  It was my impression that they were present only in cones lying on needle litter, but not in cones lying on grass.

As I was returning to my car, a woman walking by asked me about my net.  Upon hearing my explanation, she cheerfully introduced herself and asked me to tell the group she was with what I was doing.  As it turned out, this was a group from a nearby addiction recovery center, out to get some fresh air and enjoy a bit of nature (the park borders on Lake Washington).  They were quite interested to see my specimens, and asked thoughtful questions.  It was a pleasant way to end my morning.

30-Sept-2015 Lake Forest Park, Washington

Lake Forest Park cone site

Fallen cones on soil and litter

A lone Pinus nigra located at the intersection of the Burke-Gilman Trail and Ballinger Way in the city of Lake Forest Park provided me with ample cones to tap.  The cones were lying on bare soil or mixed needle and cottonwood litter.

From 50 tapped cones I collected an astounding 70 spiders and 42 harvestmen.  Ozyptila praticola was the most numerous spider species, with 3 females, 1 male and 23 juveniles present.  Enoplognatha sp. (Theridiidae) was the second most numerous spider, with 16 juveniles.  At least some of those many harvestmen were Paroligolophus agrestis.  In other words, these cones were teeming with introduced species.

Spider in its prey capture web in cone

Three introduced species in one view

The samples from Beer Sheva Park and Lake Forest Park indicate that O. praticola has spread along the entire 15 mile (23 km) length of Seattle.  I'm going to have to start looking for them farther afield. 

Terminal bud and immature seed cone from Pinus nigra tree, Beer Sheva Park