Tuesday, November 8, 2016

6-Nov-2016 Bellingham, Washington

Site location map. Click to enlarge.
I was all set to drive to Olympia to look for the introduced crab spider Ozyptila praticola, happy at the thought that traffic on southbound Interstate 5 should be light since it was a Sunday morning. But right before leaving, just to be on the safe side, I decided to check the traffic conditions. Good thing I did! An accident in Tacoma was blocking all but one lane. But northbound traffic was still moving smoothly, so Bellingham became my last-minute destination for the day.

I hadn't found any O. praticola on a recent trip to the Burlington, the closest urban center south of Bellingham, but I still thought it likely to be present in Bellingham and the northwestern corner of the state, at least along the I-5 corridor.  This is because it's been collected just over the Canadian border near Vancouver, British Columbia (see map at end of post).  So although Bellingham wasn't my original destination for the day, I didn't mind traffic conditions diverting me there.

Bellingham has no shortage of pines, I found, but there was a distinct shortage of fallen cones beneath them due to groundskeeping practices. However, after searching diligently I eventually found two collection sites, each consisting of one western white pine (Pinus monticola) with fallen cones beneath.

Lincoln Street Underpass

Site on Lincoln Street near
I-5 underpass. Pine on left.
Lincoln St. cones were barely open
A pine tree dominated the space between the the sidewalk and someone's privacy fence, and had dropped numerous cones on a thick bed of needle litter with miscellaneous bits of trash mixed in. Most of the cones were only partially open and quite wet from recent rain. And in fact my net got wetter with each cone I tapped, to the extent that I was ruing the fact that I'd left my spare net at home.  But the result was worth it: I tapped 66 spiders and 6 identifiable species from those 50 cones!

Male Centromerita bicolor tapped
from a pine cone
Tachygyna vancouverana males
For the most part, the sample composition was typical of what I've found previously in Washington's I-5 corridor: lots of juvenile Philodromus and Enophlognatha, a few Tegenaria and some adult Tenuiphantes tenuis and Tachygyna vancouverana.  What was unusual, however, was that T. vancouverana made up over a third of the sample.  They were everywhere, both males (7) and females (24). In addition, this sample contained a novelty in terms of cone tapping: Centromerita bicolor, another introduced linyphiid.  It was first found in Washington in 1975 by Rod Crawford, in Seattle.  He collected it again in 1988 in Bellingham, just a mile or so from my Lincoln Street site.  Apparently it's naturalized in Bellingham.  And finally, I tapped from these cones one juvenile Ozyptila with praticola coloring and patterning.

James Street at Whatcom Creek

My James St. pine cone
source
The James St. fallen cone
microhabitat
My second site was only about a quarter of a mile (0.4 km) to the northwest of the first site, as the crow flies.  But with daylight rapidly fading (sunset at 4:40 p.m.!), I was just happy to have found another cone source.  It was another western white pine, this time standing in the grassy area between Whatcom Creek and a parking lot.  A tangle of Himalayan blackberry (Rubus armeniacus) growing at its base had recently been cut back, making the fallen pine cones beneath accessible to me.  I often grumble about groundskeepers, but in this case they'd inadvertently done me a good turn.

Juvenile Ozyptila from James St. site
As at the first site, the scales on the cones here were poorly opened, yet they were open far enough for many spiders to have entered.  I was only able to find 25 cones to tap, but they delivered 14 spiders and one identifiable species, Phrurotimpus boralis. The rest of the sample was very much like a subset of the Lincoln St. sample including, once again, one juvenile Ozyptila with praticola coloring and patterning. As the saying goes, "so close and yet so far".

Ozyptila praticola collection sites in WA and B.C.
Blue: Confirmed with adult specimen; Yellow: Juvenile possible O. praticola;
Red: No O. praticola found. Note: B.C. records via Bennett et. al 2014

The banks of Whatcom Creek are choked with invasive Himalayan
blackberry, which incidentally originated in Armenia and Iran, not the Himalayas.

Wednesday, November 2, 2016

25-Oct-2016 Burlington, Washington

Site location map. Click to enlarge.
A very rainy October slowed my hunt for the introduced crab spider Ozyptila praticola (Thomisidae), but I was finally able to get in one solid day of searching before turning the page on the calendar.  My destination was the Burlington metro area, which includes Mt. Vernon to the south and Sedro-Woolley to the northeast.

Fallen Pinus nigra cones
In total I tapped 52 spiders from 380 pine cones (Pinus nigra, P. sylvestris, P. strobus or monticola and P. ponderosa) across 7 sites.  As readers of this blog know, I usually describe the catch from each sampling site separately.  But the results were so unremarkable and typical of what I find in fallen cones in the Interstate 5 urban corridor that I'm just going to provide a combined summary this time.

The only thomisids I found in these cones were a few juvenile Xysticus.  Thus, no Ozyptila. Tenuiphantes tenuis and Tachygyna vancouverana were the most common identifiable species present, while juvenile Enoplognatha probably-ovata and Philodromus were numerous and widespread.  A mishmash of other juvenile linyphiids, theridiids and agelenids made up the rest of the combined sample.

Rain showers and sunshine created this beautiful rainbow in Sedro-Wooley

Monday, October 24, 2016

19-Oct-2016 Plain, Washington

Site location map. Click to enlarge.
It had been nearly three months since Rod Crawford and I were last able to align both of our schedules with the weather. Too long!  But finally all the pieces fell into place and we set out once again for another day of discovery.  Our destination: Plain, a small town on the east side of Stevens Pass, just southeast of Lake Wenatchee.  A dusting of snow on the upper reaches of Baring Mountain and Mount Index -- very unusual for this time of year -- was a visual reminder of the recent passage of Typhoon Songda through the area.

No room for spiders!
We made pine cone tapping the first order of the day's business, since vegetation and litter were still wet from rain or heavy dew the previous night.  With that in mind, we made our first stop on the unnamed forested pass between the Wenatchee River and Chumstick Creek valleys.  There were ponderosa pines galore (Pinus ponderosa) and plenty of cones, but for the most part the cones were still sealed.  They had apparently fallen from the trees prematurely.

Rod sweeping herbs under my pine
cone source in Plain.
We backtracked into Plain and drove through town in search of open, accessible cones.  The best cache of cones had been dropped into a shallow roadside ditch by a lone pine growing alongside the curiously named State Haul Road.

A typical fallen ponderosa
cone in Plain
Many of the fallen cones were dusty or muddy and fairly well decayed, and none had fully open scales.  And yet, a set of 50 tapped cones produced 19 spiders from 5 families.  Six species were identifiable, including Xysticus locuples (Thomisidae), Meioneta bucklei (Linyphiidae) and the undescribed Dictyna sp. #9 (Dictynidae), which we've mainly collected from fallen ponderosa cones or associated needle litter.  The most interesting spiders in this sample, however, were the three juvenile Zodarion, presumably Z. rubidum (Zodariidae).  We first confirmed the presence of this European species in Washington only this summer, from specimens collected in western Washington.  The present specimens are the first we've collected in eastern Washington.

Scots pine on a homestead in
Little Chumstick Creek valley
Fallen Scots pine cones
Our next collection site was located in the nearby Little Chumstick Creek valley.  A local homeowner gave us permission to collect on his property, which included an assortment of introduced tree species. Among them was a Scots pine (Pinus sylvestris), so naturally I tapped another round of fallen cones.  Many cones had been crushed by driveway traffic, but I was still able to find 30 undisturbed cones among the willow leaves and pine needles off to the side. I tapped 8 spiders and 4 species from those 30 little cones! Most were mature Tachygyna vancouverana (Linyphiidae), but a female Tenuiphantes tenuis (Linyphiidae) and a juvenile Enoplognatha ?ovata (Theridiidae) were also present. Together, these three species created a very familiar assemblage.  As Rod observed, this sample could have easily been tapped from cones in the Seattle conurbation in western Washington.

Read Rod's trip narrative here.
A female Helophora orinoma (Linyphiidae) tapped from a ponderosa cone
in Plain, Washington

Fall colors on the shore of the Wenatchee River near Plain, Washington
Rod sorting a sweep sample in the Little Chumstick Creek valley

Thursday, September 22, 2016

20-Sept-2016 Marysville, Arlington and Mt. Vernon, Washington

Site location map. Click to enlarge.
Time to re-draw the Ozyptila praticola (Thomisidae) range map again!  I returned to the field this week to continue my search for the northern edge of this introduced crab spider's range in western Washington.  I had previously sampled the urban corridor along Interstate 5 as far north as Arlington (as well as several non-urban sites well beyond there), but had not found any O. praticola beyond Granite Falls.

Although I sampled in Arlington in October 2015, I considered the city under-sampled since I had only tapped one full set (50 cones) and one partial set (13 cones) of cones there.  Further, the partial set of cones had been lying in tall grass, a situation that I've found to be unattractive to O. praticola in western Washington.  So I returned to Arlington in search of at least one more set of more suitably situated cones to tap.

Arlington Denny's

A welcome sight right off
the freeway
Fallen cones on pine needle litter: a
good place to look for O. praticola
Exiting I-5 onto eastbound Route 530, the first thing I saw was a Denny's restaurant with black pines (Pinus nigra) growing next to its parking lot.  How fortuitous!  Most of the 50 fallen cones I tapped had only partially opened scales and contained significant amounts of organic debris, but also 32 spiders from 6 families.  Forty percent of them (13) were juvenile Crustulina, presumably sticta (Theridiidae), a spider I have found in fallen cones before, but rarely.  Interestingly, all 13 were from a small number of neighboring cones.  The next most common spider present were juvenile Enoplognatha ?ovata (Theridiidae), a common spider in urban cones in western Washington.  As for O. praticola, it was a no-show until I tapped my 49th cone, which produced a mature female!

Mt. Vernon

An inviting spot south of Mt. Vernon
Lots of cones but few spiders
Next stop was Mt. Vernon, a lovely little city in the Skagit delta.  I searched downtown and the industrial zone to its south for pines, and found many.  But what I didn't find were cones.  Groundskeepers had swept them all away.  It wasn't until I hit the city's southern rural outskirts that I found an accumulation of accessible pine cones.  Black pine once again, this time planted along the fence at a plant nursery.  I tapped the usual 50 cones but only got 4 spiders: all juvenile Philodromus (Philodromidae). Oh well.

Marysville Public Works

How could I resist?!
Excellent fallen cone microhabitat
at Marysville Public Works
Heading home towards Seattle, I decided to take the scenic route from Mt. Vernon through Marysville before returning to the hurly-burly of the interstate.  I'm sure glad I did!  Just a few blocks before I had to get back on I-5, I spotted a delicious row of large black pines growing along the fence line of the Public Works.  Only one tree was accessible to me, but it had dropped plenty of cones that a) had escaped groundskeepers and b) had accumulated on pine needle litter.  I was in clover.

Male Crustulina sticta. Note the
Steatoda patterning on his dorsum.
The characteristic granulations were
visible on the sternum as well as carapace
So much so that I didn't pay attention to the time (6:30 p.m.) and almost got locked into that parking lot!  I had just captured the spiders from cones 41 through 45 in my dry vial when I heard the gate being dragged closed.  That sure snapped me out of my reverie!  The employee kindly held the gate for me while I jumped in my car and zipped by, one thumb still stoppering my dry vial.  As soon as I cleared the gate I had to pull over and transfer those spiders to my alcohol vial.  Although I had only managed to tap 45 cones, I collected a whopping 45 spiders!  Twenty-six of them were juvenile Philodromus, 7 were Tenuiphantes tenuis and 6 were O. praticola.  I also captured 3 more Crustulina sticta, including a mature male.

At present, Arlington is the northern edge of O. praticola's known range in western Washington.  The search will continue...

Evening sun illuminates the Marysville water tower.

Rich farmlands of the Skagit delta were just across the
street from my Mt. Vernon site.

Saturday, September 17, 2016

A Preliminary Look At The Phenology of Adult Ozyptila praticola (Thomisidae) in Western Washington

Whenever I take a break from collecting, I'm itching the whole time to resume field work as soon as I can.  But breaks do give me time to take an unhurried look at the data I've recently collected to see whether I've learned anything unexpected.  I've been doing this with my Ozyptila praticola project data.

The goal of the O. praticola project has been simply to determine the distribution of this introduced crab spider in Washington state, as found in the fallen conifer cone microhabitat.  But in the process of pursuing that goal, I've collected some interesting life history data on the species.  In this case, adult phenology.

The Spiders of Europe and British Arachnological Society's Spider Recording Scheme ("SRS") web pages for O. praticola both report that mature males and females have been collected every month of the year in their regions of coverage. Similarly, within their local range here in Washington, I have found adult O. praticola present every month that I've searched (February through November) except for February, a woefully under-sampled month represented so far by only one 50-cone sample.

Before graphing the monthly occurrence of females and males in my collection, I standardized numbers of specimens of each sex I collected each month by converting them to a per 100 cones tapped basis.  I did this because sampling effort -- defined here as numbers of cones tapped per month -- varied greatly from month to month (see chart, right).

The resulting chart shows that female O. praticola have been present in my samples in fairly consistent concentrations of about 1 to 2 spiders per 100 cones every month I've sampled (excluding February, as previously discussed).  In contrast, I found males in tapped cones only in spring (April & May) and fall (September & October), and at varying concentrations.

Adapted from British Arachnological Society's
Spider Recording Scheme
Although SRS reported O. praticola males present every month, it also showed a bimodal distribution with more males having been collected in May & June and, to a lesser degree, in September, than any other month (see chart, right).  Unfortunately, it is not possible to know whether this apparent similarity in patterns between my data and data reported by SRS is meaningful since it seems doubtful that the SRS data were standardized for sampling effort, as mine were.  The SRS results could be explained simply by more British spider collectors being active in spring and fall than other seasons.

Note that my phenology chart is based on preliminary data from a study not yet completed.  So far, I've tapped 268 O. praticola from 1,895 conifer cones.  Of those 268 O. praticola, 29 (11%) were female, 14 (5%) were male and 225 (84%) were juvenile.  That's not a lot of specimens to base any conclusions on.  Still, it's more data than we had a year ago, which was almost nil.  I am excited to know whether the patterns in my chart will change with the addition of more data.  And so, as usual, I am itching more than ever to get back out into the field.

Saturday, August 27, 2016

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

Wednesday, August 24, 2016

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