Are Douglas-fir Cones As Depauperate In Spiders As They Appear?

Site location map. Click to enlarge.

The other day I tapped cones at two more sites near North Bend, Washington for my Ozyptila praticola project.  No pine cones being available, I tapped 50 Douglas-fir (Pseudotsuga menziesii) cones at each site and found only 1 spider in one set and two spiders in the other.  I've tapped enough Douglas-fir cones over the past year or so to have formed the impression that they seldom hold many spiders.  But is this really true?  I decided to run the numbers and find out.

Since I began my Ozyptila praticola project in May 2015, I've tapped 31 sets of black pine (Pinus nigra) cones and 35 sets of Douglas-fir cones.  These are two of the three species of cones I've tapped most frequently for this project, and they have similarly sized cones.  (Western white pine, P. monticola, is another frequent cone source but has significantly larger cones, so I excluded it from this analysis.)  Most sets consisted of 50 cones, but since not all did I standardized my data by using average number of spiders per cone per set in my calculations.  All cones tapped were from low-elevation (< 300 m) sites in western Washington.

A Douglas-fir cone: boring but worthy of tapping!

My impression about spider density in Douglas-fir cones was correct; there was a significant (P < 0.0001) difference in the average number of spiders per cone in black pine and Douglas-fir cones, a two-tailed student t-test showed (t = 4.0682, df = 64).  Black pine cones had an average of 0.28 spiders per cone, whereas Douglas-fir cones had only 0.10 spiders per cone on average, an almost 3-fold difference.

I've collected about 20 species of spiders each from black pine and Douglas-fir cones.  (A few specimens still await identification, so the exact number of species may change, but not by much.)   There are 11 species in common to the black pine and Douglas-fir cone lists.

My conclusion is that Douglas-fir cones are indeed low in number of spiders relative to black pine cones, but they're equally species-rich.  Their low relative spider frequency makes Douglas-fir cones less exciting to tap, but they're still very much worth tapping!

Oh, for those keeping track, none of the three spiders I tapped from cones near North Bend the other day were O. praticola.

View of Rattlesnake Ledge from Cedar River Watershed Education Center

23-Aug-2016 Carnation, Washington

Site location map.  Click to enlarge.
Key: Blue - Ozyptila praticola confirmed, Yellow - O. praticola suspected,
Red - No O. praticola found

Yesterday I returned to my search for the introduced crab spider Ozyptila praticola (Thomisidae).  Since I've already found it in two places in the Snoqualmie River valley (Snoqualmie and Duvall), I wanted to continue my search into the foothills of the Cascades mountains east of the river valley.

Maybe not the best place to collect spiders...

My focal point was the Tolt Reservoir.  On a mountain biking website I had found a detailed description of a circular route to near that point which started in Tokul and ended near Duvall.  What a windfall!  Or so it seemed until I tried driving it.  Not too far beyond Tokul, the roads were gated and posted with warning signs about written permission being required before entering.  This approach being unavailable, I decided to try driving the final segment of the route "backwards" from Duvall.  Whether that approach is open to the public I still don't know, since road names on the signs and in the instructions didn't always match up, and I didn't have all the maps with me that I thought I had.  It was one of those days...  I'll have to return another time better prepared.

Cone source, a lone pine

A fallen cone

But the day wasn't a total loss since I was able to find cones to tap in Carnation and confirm that O. praticola is present at the midpoint of the Snoqualmie River valley.  The cone source was a black pine (Pinus nigra) growing on a street corner in the business district.  Its fallen cones were on a bed of pine needles through which sparse herbs were growing.  Tapping 50 cones I collected 18 spiders, 10 of them O. praticola.  Other spiders present in these cones included a Diplostyla (Linyphiidae) female and penultmiate male, a pair of mature Tenuiphantes tenuis (Linyphiidae) and two juvenile Clubiona (Clubionidae).  The cones also contained 25 harvestmen and a number of tiny snails.

A wall of corn marks the edge of town in Carnation

27-July-2016 Mount Zion, Washington

Site location map. Click to enlarge.

We left Seattle a little earlier than usual in order to catch the 9:40 a.m. Edmonds-Kingston ferry, only to find it delayed by fog.  Well, that gave Rod Crawford and me plenty of time to talk over our collecting strategy for the day.  Our destination was Mount Zion, located a few miles northwest of Quilcene in Clallam County.  This would be my first opportunity to tap pine cones in Clallam Co.

A day for fog horns

Gnome-plant in bloom on
the dark forest floor

The Mount Zion trail must be magical to hike in the spring, when the rhododendrons are in bloom.  Rhodies are a major part of the forest understory here, growing 8-10 feet tall and in places probably creating a sort of "flowered tunnel" effect.  This time of year, nothing so showy was happening.  However, two intriguing myco-heterotrophic plant species were blooming subtly on the forest floor, woodland pinedrops (Pterospora andromedea) and gnome-plant (Hemitomes congestum).

Pine with a deceptively white
trunk

Pinedrops backlit by
a setting sun

After reaching the summit, I continued hiking along the ridge towards the southeast where some cliffs were supposed to provide an excellent view as well as, I hoped, a different spider fauna from what we were finding in the forest.  About half way to that point I was delighted to spot some western white pine (Pinus monticola) cones next to the trail.  It took me a few minutes to locate the tree dropping them because, like I'd found near Square Lake in neighboring Kitsap County, the trunk was uncharacteristically white with what I presumed were epiphytic lichens.  If I hadn't seen the cones around it or noticed the whorled branching pattern, I probably would have mistaken it for an alder.

Callobius nomeus female with egg sac
on a cliff face in the forest

Fallen cone microhabitat

I tapped 50 cones and collected 7 spiders and 3 species.  All three were common litter species, but one of them, Walckenaeria cornuella (Linyphiidae), I had never tapped from fallen conifer cones before.  And, this was the only microhabitat we collected it from this day.  In addition to spiders, these cones also contained native harvestman and centipedes.

Snail on cliff face in forest

Female Zygiella dispar with spiderlings
on a sign at the trailhead

The trail was remarkably silent the entire day.  No rushing water, no crickets, no cicadas, no birds except for one raven, no mammals except for one barking chickaree and a few passing humans.  And no airplanes flying over or highway traffic rumbling in the distance.  Just wind.  It was one of the most silent trails I've ever been on.

This rock dove (Columba livia) joined us for the morning ferry crossing to Kingston