Wednesday, December 16, 2015

15-Dec-2015 U-W Campus, Washington

Site location. Click to enlarge.
The weather forecast wasn't looking promising for a full day in the field at any of Rod Crawford's target sites, so instead I spent an hour tapping cones on the nearby University of Washington campus in Seattle.  The campus sports numerous eastern white pines (Pinus strobus) as well as other exotic pine species.  In some places their fallen cones are allowed to accumulate, creating habitat for spiders and other invertebrates.

Sample site, Hutchinson Hall on right.
The fallen cone microhabitat, with
cigarette butts.
For years I've been developing a mental map of pine cone deposits on campus.  The site I sampled this day, located between Hutchinson Hall and the adjacent tennis courts, was one of the first I noted years ago as I walked through campus from the Burke Museum to my bus stop by the HUB.  Four mature eastern white pines stand in a row along the sidewalk that runs the length of the area.  No shrub layer or ground cover grow here, and the litter consists of a thin veneer of pine needles and the occasional oak leaf.  The area seems to have two main functions: as a pedestrian shortcut through the tennis courts, and as a place for people in Hutchinson Hall to grab a smoke.  Cigarette butts outnumbered fallen cones near the hall's southeastern door, and there were a lot of cones...

Female Tachygyna ursina (left)
and T. vancouverana (right)
Juvenile theridiid
Air temperature never exceeded 40 F while I was there (brrr!), but this didn't seem to impede the movement of the linyphiids that hit my net.  Of the 6 spiders I tapped from 50 cones, 4 of them were linyphiids: Tachygyna vancouverana and probably Tachygyna ursina (still to be confirmed).  The other two spiders were a juvenile dictynid and a juvenile theridiid that could very well be a Platnickina tincta (=Theridion tinctum).  These are all spider species that I've tapped previously from pine cones in western Washington.

Interestingly, I found no spiders in the cones I tapped in the middle of the plot.  All spiders came from cones lying within a few inches of the building or the tennis court wall.  Was this random chance, or was it due to differences between the "inner" and "edge" cones in microclimate or predation pressure or some other factor?
Another view of the sample site.

Saturday, December 12, 2015

9-Dec-2015 Fircrest, Washington

Site location. Click to enlarge.
This time of year, field trips don't always turn out as planned.  With the Puget Sound region in the midst of a multi-day series of rainstorms, I knew that it was a big gamble to attempt any field work.  But I was antsy to get back outside, so I decided to see what I could accomplish in an afternoon with less than 50% chance of rain predicted. Greater Tacoma was my destination because it is the next metropolitan area south of Federal Way, the southern-most place I've found the introduced crab spider Ozyptila praticola (Thomisidae).

"It might be raining where you are."
A southbound lane on Interstate 5 was closed due to flooding right before my exit in Fife.  This was pretty emblematic of the day: local flooding.  And intermittent downpours.  The ground was so saturated from days of rain that water was pooling and even fallen cones protected by tree foliage above were sopping wet.  Really wet cones are difficult to tap because they quickly saturate my net, which becomes muddy.  This makes it hard to see expelled spiders, especially spiderlings.  Next time I venture out on a wet day, I'll come prepared to collect cones into containers so that I can process them later, after they've dried a bit.

Sample site
Fallen cones
Anyhow, given the conditions I was finding, I decided to forego collecting and just reconnoiter the area for cone deposits that I could return to to sample some other, drier day.  Driving the 10 miles between Fife on the east side to University Place on the west side, I found several accumulations of cones.  Most of them were dropped by the exotic black pine (Piuns nigra), so when I spotted a huge native western white pine (Pinus monticola) in Fircrest, I couldn't resist tapping as many cones as my net would allow.

Female Lepthyphantes leprosus
Lepthyphantes leprosus epigynum
I was only able to find 10 cones in the public right of way, but my net quickly became too much of a mess to handle more anyways.  From them I tapped 3 spiders and 3 species, the only identifiable one being a female Lepthyphantes leprosus (Linyphiidae).  When I return in drier weather I hope I can get permission from the landowner to tap the dozens of additional cones lying on private property, because this appears to be a promising trove.

Besides coming away with a list of promising cone sampling locations for my next foray, the trip turned out to be useful in improving my knowledge of local geography.  Until now I didn't realize how big the Puyallup River is because it's scarcely visible from I-5, and I'd always flown across it without even realizing it!  Seeing it in flood stage from a local bridge caused me to add it to my mental list of potential natural barriers to the southward spread of O. praticola.
View of Puyallup River from Eells St. bridge on July, 2015. Screen grab from Google.

Saturday, December 5, 2015

1-Dec-2015 Tacoma Mall, Washington

Site location. Click to enlarge.
On my most recent trip in search of the southern boundary of the introduced crab spider Ozyptila praticola (Thomisidae) in Washington state, I had leapfrogged over Tacoma and drove directly to DuPont and Lakewood, which I thought might lie in the southern reaches of the specie's local range.  Finding no O. praticola at the sites I sampled in those cities, it made sense to backtrack to Tacoma for my next sample.  Tacoma is the next major city south of the southern-most place I have confirmed O. praticola's presence (Federal Way).

Sample site. Screen grab from Google Street View.
On the drive to DuPont a few days prior, I had glimpsed several large pine trees growing around businesses near the Tacoma Mall.  Although I encountered the usual problems with most of them (cones and tree litter had been removed by groundskeepers, or fallen cones were present but not open), I did eventually find a row of shore pine (Pinus contorta) and Scots pine (Pinus sylvestris) trees planted along a stone wall supporting the raised parking lot for Macy's Furniture Gallery.  Unfortunately I have lost the photos I took at the site, but this screen grab (left) from Google Street View will suffice.  Note that there was more needle littler on the ground than is evident in this photo, but it was quite thin.

Although I was able to find 41 open or semi-open cones to tap, I found only two arachnids in them: 1 juvenile Enoplognatha probably-ovata spider, and 1 adult Paraligolophus agrestis harvestman.  Both are introduced species.  This was perhaps my most uninteresting cone sample to date.

At the moment, Federal Way remains the southern-most confirmed location of O. praticola in Washington state.  The search continues...

The spiders are out there.

29-Nov-2015 Salsbury Point Park, Washington

Site location map. Click to enlarge.
The dry spell continued long enough to provide Rod Crawford and me another opportunity to make another late-fall collection.  As our destination Rod chose Salsbury Point Park, a small county park located near the foot of the Hood Canal bridge on the northern end of the Kitsap peninsula.  It sounded like a good destination to me, since it would require much less driving than most of our trips, and according to photos on the county's website, it had pine trees.  If cones were available under those pines, I would be able to collect my first-ever cone spider sample in Kitsap County.

Fog makes for fanciful ferry crossings
Hood Canal bridge viewed from park
One of the reasons Rod selected the site was because sunshine was forecast there, and because of its western exposure.  As it turned out, fog blanketed the region for the entire day and temperatures never got above the mid 40s.  Besides creating chilly work conditions, the lack of sunshine meant that ground-active spiders weren't out.  Nevertheless, with the help of new field volunteer Ben Diehl, we managed to find plenty of spiders.  And, there were indeed cones under the pine trees!

Two of the park's several shore pines
Spongy leaf and needle litter
The park has several clumps of shore pine (Pinus contorta) planted around buildings and in little islands in the lawn.  Although a groundskeeper was busy blowing leaves, etc. when we arrived, I had no trouble finding open cones under many of the pine trees.  I rather enjoyed crawling under the trees' low branches to reach the cones.  The pine needle litter was soft and, in one area, quite spongy with vine maple leaves.  And it was much drier than the surrounding lawn.

Many cones got eaten by Douglas
squirrels (Tamiasciurus douglasii)
before they could fall
Showy erigonine juvenile
I tapped 100 cones and collected 18 spiders.  Half of them were juvenile erigonine linyphiids with dark bodies and orange legs - very showy in my net.  The only species identifiable in my cone sample was the undescribed Tachygyna sp. #4 (Linyphiidae).  I tapped 4 females and 1 male from the cones.  Rod and Ben also collected the species from beach meadow grass, ferns and conifer foliage.  Interestingly, I did not find it in the associated needle and leaf litter that I sifted.  The only spider I found in common to both microhabitats at the site was juvenile Enoplognatha that look like ovata (Linyphiidae).

Be sure to check out Rod's take on the day here.

Douglas squirrel with a mouthful of bark that I watched it strip from
the trunk of this western red cedar (Thuja plicata)

Wednesday, December 2, 2015

28-Nov-2015 Lakewood and DuPont, Washington

Locations of present and previous
Ozyptila praticola sample sites. Click to enlarge.
Last week I confirmed the presence of the introduced crab spider Ozyptila praticola (Thomisidae) in the city of Federal Way, Washington.  This day I looked for it in Lakewood and DuPont, which occupy what I have theorized may be the southern end of its local range.


Fallen white pine cones in Lakewood
Lakewood site
My Lakewood sample site was in the Tillicum neighborhood, which is sandwiched between American Lake and Joint Base Lewis-McChord.  Two western white pines (Pinus monticola) located along the edge of a suburban yard had dropped cones onto a variety of substrates including pine needle and oak leaf litter, English ivy (Hedera helix) and decorative stones. I tapped 51 cones and collected 9 juvenile spiders.  Most were Enoplognatha sp. (Theridiidae) and Phrurotimpus sp. (Phrurolithidae).  None were crab spiders.


Next I drove about 5 miles further south to DuPont.  My hope was to tap cones dropped by the pines shading the sidewalks in front of the Amazon Fulfillment Center and Intel Corporation.  These trees were clearly visible from aerial photos.  What I found at the site, however, was that all forest debris had been removed from the ground beneath the trees.  This included cones.

DuPont site
Fallen black pine cones in DuPont
Returning to a shopping center that I had passed on the way to my preferred site, I discovered a row of black pines (Pinus nigra) planted as a visual buffer between the road and a parking lot.  Although most of the cones that had fallen there had also been whisked away by groundskeepers, a few had escaped that fate by rolling into an undeveloped lot.  And most had come to rest on leaf or needle litter, which is a habitat amenable to O. praticola.  But tapping 44 cones, I collected only 2 spiders.  One was a male Cryptachaea (Theridiidae), the other an unknown juvenile.  Again, no crab spiders.

This was not a very exciting cone tapping day.

Mt. Rainier was barely visible through the cold fog