30-April-2018 Tacoma, Washington

Site location map. Pins and cross indicate cone and
litter samples, respectively.

After recently finding juvenile Ozyptila on the campus of University of Puget Sound, I was convinced that the introduced crab spider Ozyptila praticola (Thomisidae) was present there. But I lacked a mature specimen to prove it. I thought that Rod Crawford or I might turn one up during the Point Defiance Park BioBlitz, especially in the anthropogenic southern part of the park, but that didn't happen. So I returned to north Tacoma this day to sift more litter from the university's "Ozyptila hot spot", and tap more fallen cones until I found a mature Ozyptila (of whatever species).

I debated whether to begin my day sifting litter or tapping cones. Since Rod and I had spotted some nice cone deposits near Pearl and 21st on our way to the BioBlitz a few days before, I decided to tap cones first. As eager as I was to sift litter at the Ozyptila hot spot, I didn't want to risk losing good cones to groundskeepers. I have occasionally seen them removed before my very eyes. It is a story almost too sad to tell...

In total, I tapped 250 pine cones: 150 black pine (Pinus nigra) cones from three sites, and 100 western white pine (P. monticola) cones from two sites. Though each set of cones produced a set of spiders unique in composition, taken together they provided a fairly typical urban sample. From the 250 tapped cones I collected 76 spiders and 9 identifiable species. A few points of interest:

• I tapped female Rugathodes (Theridion) sexpunctatum from cones at two sites. It's a common enough native spider -- we collected it in multiple microhabitats in Point Defiance Park, for example -- but I had only found it in the fallen cone microhabitat twice before in western Washington. So the present samples doubled my cone tally.
• Cryptachaea blattea is an introduced theridiid that I've tapped frequently from cones in western Washington, from Pierce County in the south to Skagit County in the north. But today it seemed especially prevalent; I tapped it from cones at three of the five sites.
• Another introduced crab spider, Philodromus dispar, is a species I tap frequently from cones in western Washington, albeit usually as juveniles (penultimate males can be distinguished from congeners by their round palps). This day, however, I tapped several mature males from cones. Checking my records, I found that the four other times I tapped males from cones were in the first two weeks of May, quite consistent in timing with these April 30th samples in Tacoma.
• No O. praticola!

"Dirty" Arbutus litter full of fines...

...including a fine female O. praticola!

Having found no O. praticola in the cones, I returned to the Ozyptila hot spot to sift litter. I first sifted a net-full of oak leaf litter because I knew it would be "clean". That is, it would be easy to examine the siftings because the litter was relatively free of dirt and organic particles small enough to fall through the sifter. The oak leaf litter, however, produced no O. praticola, not even juveniles. Next I switched to litter under the Arbutus unedo shrubs from which I'd originally captured juvenile O. praticola in cardboard live traps. This batch of litter consisted of A. unedo leaves, heavily decayed wood chip mulch, and Douglas-fir (Pseudotsuga menziesii) needles, which are quite short. In other words, "dirty" litter that largely fell through the sifter. Lucky for me, along with it fell a female O. praticola, hurray! 

Ozyptila praticola is now confirmed as present in Tacoma. However, its present distribution appears to be extremely localized.

The many places I've looked for but not found Ozyptila praticola
in Tacoma (red), and the one place I have (blue).