16-Aug-2017 Mount Vernon and Bellingham, Washington

Site location map. Click to enlarge.

Ever since finding juvenile Ozyptila that were patterned like praticola at two sites in Bellingham last November, I've been wanting to return to search for adult specimens. I wanted to know conclusively whether this introduced thomisid was present in Whatcom County's biggest city. It seemed likely, given Bellingham's situation along Interstate 5 and its proximity to British Columbia's southern reaches, where O. praticola has also been found. This would be the day to find out! But first, on my way north from Seattle to Bellingham, I stopped in Mount Vernon and Bow to take a few more samples in Skagit County; I have yet to find O. praticola (or any Ozyptila) in fallen conifer cones in Skagit County.

Mount Vernon & Bow

Anderson Rd site

Lots of cones & litter under the shrubs

On past trips north I'd noticed a row of pines growing just east of the freeway near the Anderson Road exit. Upon closer inspection this day, I found that groundskeepers had removed all of the cones and needle litter from beneath them. But it didn't take long to find "greener pastures" on the other side of the freeway: black pines (Pinus nigra) planted along a parking lot perimeter. Groundskeepers had been busy there too, but hadn't gone so far as to remove cones and litter from beneath the shrubs.

Zodarion collection sites.  Blue = Zodarion rubidum adult;
Yellow = juvenile Zodarion 

I tapped 50 cones and collected 37 spiders from four families. Most were juvenile Steatoda (Theridiidae) and Philodromus (Philodromidae). The only identifiable species was Tenuiphantes tenuis (Linyphiidae). By far the most interesting spider in the sample was a juvenile Zodarion (Zodariidae), presumably Z. rubidum. This is the farthest north I've found this rapidly spreading introduced species. I also sifted pine needle litter, but didn't find anything new. I found no O. praticola in either microhabitat.

Bow Hill Rest Area

Bow Hill Rest Area along Interstate 5 provided another convenient spot to tap cones in Skagit County. The facility is situated in a fairly natural forest fragment dominated by western red-cedar (Thuja plicata) and Douglas-fir (Pseudotsuga menziesii). Nevertheless, the 50 Douglas-fir cones I tapped produced only two harvestmen and two juvenile linyphiids.

Bellingham

Lincoln St. site

Since I already knew that Ozyptila could be found at the two Bellingham sites I had sampled previously, I decided to intensively re-sample those sites before looking for new ones. My first stop was the western white pine (Pinus monticola) growing on Lincoln St. near the Interstate 5 underpass. Except for the need to wade through thorny Himalayan blackberry (Rubus armeniacus), I had no trouble finding 50 fully opened cones to tap.

Female Steatoda bipunctata

Those 50 cones produced an astounding 100 spiders, 64 of which were the introduced Steatoda bipunctata (Theridiidae). I also collected two female Eratigena agrestis (Agelenidae), commonly known as hobo spiders. Juvenile agelenids aren't uncommon in the fallen cone microhabitat, but this is the first time I've collected mature E. agrestis. I suspect the reason is that most cones that I tap don't provide large enough hiding places for Eratigena adults, which have body lengths of 11-15 mm (legs not included). As for O. praticola, I again found but one juvenile spider at the Lincoln St. site. My plan had been to sift litter if I didn't find an adult specimen in the cones, but I decided against it unless my second Bellingham site proved equally unhelpful. The reason was the poor dog on the other side of the fence that had been barking for the past hour and a half. I was sure that I, it and its neighbors would enjoy a reprieve.

This unassuming site on James St. ...

...harbored this male Ozyptila praticola

Moving on, I was pleased to find that the western white pine at the intersection of Whatcom Creek and James street also had numerous fully opened cones beneath it. I tapped 50 cones and collected 24 spiders from 5 families. Only two species were identifiable: T. tenuis and, O. praticola! So now we know with certainty; Ozyptila praticola is indeed present in Bellingham.

Status of Ozyptila praticola in western Washington. Blue, yellow, or red
indicate adult O. praticola, juvenile Ozyptila sp. or no Ozyptila found, respectively