Friday, January 22, 2016

20-Jan-2016 Second Population Of Pseudeuophrys lanigera (Salticidae) Found In Washington State

Pseudeuophrys lanigera collection sites
in Washington, USA
Last fall I discovered a male and several juvenile Pseudeuophrys lanigera jumping spiders in pine cones lying in an industrial back lot in Mukilteo, Washington.  Since mine was the first reported discovery of this European species in North America, I was eager to determine whether the species was naturalized in the area, or whether I had found a dead-end population.  But then winter weather set in, so I postponed follow-up sampling until spring.

As luck would have it, I didn't have to wait that long to revisit the P. lanigera question.  Betsy Bruemmer, Collections Manager at the Museum of History and Industry (MOHAI) in Seattle contacted Rod Crawford last week because she'd noticed several tiny spiders in the MOHAI Resource Center, MOHAI's administrative offices and storage facility located in Seattle's Georgetown neighborhood.  The photos she sent of some of the individuals she'd captured on sticky traps sure did look familiar - like P. lanigera!  Rod and I couldn't resist requesting a tour of the facility, and Betsy very kindly obliged.

Right P. lanigera palp,
ventral view. Spider
dead when collected.
Right Pseudeuophrys lanigera palp,
semi-lateral view. Spider dead when
Although we didn't find any live, free-ranging P. lanigera during our visit as we'd hoped, Betsy was able to give us a specimen that she'd recently captured live and preserved in alcohol.  She also pointed out another still-alive individual stuck to a sticky trap that Rod was able to extricate, and found a dead but intact individual on the floor.  Rod examined the live-captured specimens, while I examined the one that was already dead when collected.  They all turned out to be mature P. lanigera.

Dead & desiccated but still identifiable
Betsy had made several interesting observations about this population of P. lanigera.  First, all the specimens were captured in windowless storage rooms that are frequently dark.  Second, there is some suggestion that these animals may have used the walls to guide their movements since so many were intercepted by sticky traps, which were situated on the floor along walls.  In addition, Betsy found the specimen that I examined (and whose right palp is pictured here) dead on the floor next to the baseboards.  This is all in great contrast to the population I found in Mukilteo ("SW of Paine Field" on the map above), which were tapped from pine cones laying outside in an open lot.  However, both populations were found in areas of light industry and warehouses.

Considering that the Mukilteo and Seattle sites are 24 miles (39 km) apart, it seems likely that P. lanigera is resident in the greater Seattle area.

Update (25-Jan-2018): You can read our subsequent paper about P. lanigera in Washington state here or here.

Rod and Betsy examine one of the (highly magnified!) jumping spiders captured in a sticky trap

Friday, January 8, 2016

6-Jan-2016 Discovery Park, Seattle, Washington

Site site location. Click to enlarge.
Daytime rain and overnight frost had been dissuading me from tapping cones for several weeks.  But with a few preceding nights above freezing and this day a sunny 48 F (~9 C), conditions were once again amenable to taking a winter cone spider sample.

Sample site
A western white pine (Pinus monticola) growing at the edge of a Douglas-fir (Pseudotsuga menziesii) woods in Seattle's Discovery Park was my cone source.  All of the cones I tapped were lying on needle-and-twig litter within the tree's drip line.

Fungus and a fallen cone
I tapped 50 cones and collected 20 spiders and 6 species.  Three were species I find commonly in Seattle-area fallen cones: juvenile Cryptachaea blattea (Theridiidae), juvenile Enoplognatha probably-ovata (Theridiidae), and female Tachygyna vancouverana (Linyphiidae).  However, the other 3 species in my sample were new to me.

Adult Blabomma californicum
Blabomma californicum epigynum
Almost half of the sample was comprised of Blabomma californicum (Dictynidae).  With females measuring 6 mm in length, this is by far the largest dictynid I've handled.  I'm more accustomed to the smaller dictynids found in webs at the apices of herbaceous plants, so finding (with the help of Rod Crawford - thanks Rod!) that these were dictynids was a surprise and learning experience for me.  Well, every cone sample is a learning experience, but some more than others.

I'm a linyphiid. Good luck IDing me.
I have 2 more species of linyphiids still to identify, but that will have to wait for another day.

Although a merry sun was shining, the constant north wind kept me chilled.  But it was apparently fine weather for ballooning for numerous spiders in nearby Douglas-fir trees.  Glistening strands of silk 1-2 meters long were stretched horizontally on the wind from the ends of branches on the sun-soaked south side of the trees.  Unfortunately I was unable to intercept any of the attached spiders, so I don't know who was responsible for the eye-catching display.

Juvenile Blabomma californicum. Until I knew what these were, I was
calling them "tigers", for obvious reasons.  Beautiful spiders.