Friday, April 8, 2016

5-Apr-2016 Cottage Lake and Duvall, Washington

Site location map. Click to enlarge.
Having had no luck finding the introduced European crab spider Ozyptila praticola (Thomisidae) south of Federal Way, I decided to turn my search eastward.  My jump-off point was Woodinville, where I collected numerous juvenile O. praticola last year.  I stopped in Cottage Lake for my first cone sample, then crossed the Snoqualmie River into Duvall for my second.

1.  Cottage Lake
Black pines behind the Safeway
in Cottage Lake
Fallen cone microhabitat
behind the Safeway
I gravitate to business districts when searching for Ozyptila praticola because pine trees tend to be more prevalent in them than elsewhere.  The small shopping center on Woodinville-Duvall Road in Cottage Lake was no exception.  In fact, it exceeded my expectations because black pines (Pinus nigra) completely lined two of its sides.  And while groundskeepers had removed much of the needle litter and, presumably, many cones, I was still able to find 64 cones to tap. Some cones I tapped were lying on a very thin layer of needles or on moss, but most were on bare ground.

Male Bassaniana utahensis
Those 64 tapped cones produced 14 spiders for an absolutely average spiders per cone ratio of 0.22.  Three species were identifiable, two of them native: the crab spider Bassaniana (a.k.a. Coriarachne) utahensis (Thomisidae) and the tiny Tachygyna ursina (Linyphiidae).  I've tapped B. utahensis from cones in eastern Washington before, but this was the first time I'd done so in western Washington.  This specimen will become the first in the Burke Museum's collection from King County.  The other identifiable species was O. praticola.

2.  Duvall Park & Ride
Western white pines flanked this
building next to the Park & Ride
Some very productive cones were
hiding under this hedge!
Crossing the bridge into Duvall, I couldn't believe my good luck at immediately spotting western white pine trees (P. monticola) flanking a small business next to the Duvall Park & Ride.  Most of the pines were lining the driveway down to the P & R, making access to their fallen cones quite easy.

At first it didn't look like I'd be able to find a full sample of 50 cones to tap, but the more I searched, the more cones I found.  One of the most productive caches was underneath a hedge growing curbside in front of the business.  The cones were lying on a wide variety of substrates, including pavement, soil, uncut grass, and plant litter beneath the hedge.  I tapped 64 cones and collected 32 spiders, well above twice the average density! 

Clocking in at 14 juveniles, Enoplognatha probably-ovata (Theridiidae) was the most common morphospecies present.  Ozyptila praticola took second place, with 7 juveniles, followed by Phrurotimpus sp. (Phrurolithidae) with 4.  I also collected a very teneral Lepthyphantes male which I haven't identified yet.  But the most esoteric specimens in the sample were two juvenile Tibellus sp. (Philodromidae)!  This is one of the most common spiders found around here...on tall grass.  Not surprisingly, these came from the cones I found laying in tall, unmowed grass.

Clearly I have not yet found the eastern extent of O. praticola's local range. The search will continue eastward into the Cascades lowlands!
View of the Snoqualmie River from the Duvall bridge

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