Thursday, July 20, 2017

16-July-2017 Granite Falls and Lake Roesiger, Washington

Collection sites of mature Ozyptila praticola (blue) and
O. pacifica (yellow). The red pin marks the location
of Granite Falls. Ozyptila pacifica data courtesy of
Burke Museum of Natural History and Culture.
Back in May, 2016, I tapped pine cones in Granite Falls for my ongoing study of the distribution of the introduced crab spider Ozyptila praticola (Thomisidae) in Washington state. Frustratingly, what I found there were juvenile Ozyptila. Although I suspected that they were O. praticola, I can't rule out the possibility that they were the native species O. pacifica (or some other species) since the Washington ranges of O. praticola and O. pacifica overlap (see map, right). I returned to Granite Falls this month in hope of collecting mature Ozyptila.

Site location map. Click to enlarge.
I tapped cones at two sites in Granite Falls, then drove south to Lake Roesiger Park to tap an additional two sets. Both locations are in the foothills of the Cascade Mountains. I'm looking to see if there is evidence that O. praticola has crossed that threshold.

Granite Falls

Pine cone source at car wash
Cozy nest of pine cones and needles
My first site in Granite Falls was the car wash on the east side of the business district. I had eyed this spot numerous times as I passed it on the way to Mountain Loop Highway and the innumerable hiking destinations beyond. The site has a planting strip that includes a black pine (Pinus nigra) tree surrounded by dense shrubs. Fallen needles and cones get ensconced in the shrubs, escaping removal by groundskeepers. I tapped 110 well-opened cones but collected mainly juvenile harvestmen (18!). Of the 7 spiders present, only Platnickina tincta (Theridiidae) was identifiable to species and the only crab spider in my sample was a Philodromus. Although spiders were relatively few there, I certainly enjoyed friendly conversation (and permission to continue!) with the owner of the car wash and others who happened by as I was working.

My second site in Granite Falls was in a residential area a few blocks from the car wash. I tapped 100 fallen Pinus monticola cones that had come to rest under a rhododendron hedge and collected 38 spiders from 6 families. Four species were identifiable, but the most common spiders were juvenile Tegenaria (15) and juvenile Steatoda (11). The Ozyptila count here: 1 juvenile and 0 adults. That's even more frustrating than the 3 juveniles I collected in 2016. It's the curse of the juvenile Ozyptila! I decided it was a good time to stop for a delicious and very satisfying late lunch at Barbeque Bucket before proceeding to Lake Roesiger.

Lake Roesiger Park

Site 1 at Lake Roesiger Park
I tapped my first set of Douglas-fir (Pseudotsuga menziesii) cones beneath a small grove of trees right by the lakeshore. It was quite pleasant to smell the fresh lake air and hear people frolicking in the water as I tapped 100 cones. The exercise produced a multitude of harvestmen but only 9 spiders, most of which were Cryphoeca exlineae (Agelenidae).

Site 2 cones on needle and
maple leaf litter
Site 2 at Lake Roesiger Park
My second set of cones came from the forest edge opposite the parking lot with respect to the lake. Here, 50 tapped cones produced only two juvenile spiders, a Callobius (Amaurobiidae) and a gnaphosid. I found no Ozyptila in either set of cones.

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