How widespread is Euryopis formosa's relationship with pines?

Click to enlarge. [source]

Rod Crawford and I noted in our recent paper that virtually every Euryopis formosa (Theridiidae) specimen collected in Washington state has been collected in the vicinity of ponderosa pines (Pinus ponderosa) (see map, right).  Our observation was consistent with Gillette et al. (2008), who identified E. formosa as a significant indicator of old-growth status in a pitfall study of the ground-dwelling spiders in P. ponderosa stands in the Cascade Range of California.

Since Euryopis formosa occurs from "Central California north to British Columbia and east to Wyoming" according to Levi (1954), these findings left me wondering whether E. formosa is associated with pines over its entire range, or whether the apparent association is only a Cascades phenomenon.  To begin answering this question, I decided to do a back-of-the-envelope analysis by mapping E. formosa specimen locations reported in Levi (1954) and Bennett at al. (2014) along with those Rod Crawford and I reported on from Washington.

Presence or absence of pine
(Pinus) at E. formosa collection sites

I obtained coordinates for the published locations from USGS's Graphic Names Information System and Google maps, then determined the presence/absence of pines (of any species that drops open, intact cones) in the area using a combination of Google Street View, E-flora B.C. and Calflora.  I mapped the results using GPSVisualizer.  Note that since the specimens listed in Levi (1954) were collected in the late 19th or early 20th century, sometimes from poorly defined locations (e.g. "Jackson County"), I can't be certain that I've correctly identified every location or correctly guessed the forest type growing there at the time of collection.  Hence, "back-of-the-envelope".  Given those caveats, here is the result.  Green markers indicate specimens collected in places where pines were likely to be present at the time of collection.  Collection sites within about 5 miles of pine-containing forests are marked in blue, while sites thought to be devoid of pines are marked in red.

It appears that the spider-pine relationship holds true in the core of E. formosa's range, but less reliably so on the edges. Of course, no firm conclusion can be drawn from this surface analysis.  For that, one would need to get updated specimen data from relevant spider repositories and superimpose it on range maps of pines that drop open, intact cones.  It would be a fair amount of work, but it looks like a worthwhile project.

10-Aug-2015 Lumberman's Monument, Michigan

Site location (click to enlarge)

Red pine forest

Michigan is now on the World Map of Pine Cone Spiders, joining the US states of Washington, Oregon, California and Massachusetts, and the province of South Holland in The Netherlands.  I had the opportunity to tap two species of fallen pine cones at Lumberman's Monument in Michigan's Huron-Manistee National Forests earlier this week, and found spiders in both sets.

Red pine cone

White pine stand

I tapped 50 red pine (Pinus resinosa) cones from the woods near the Monument campground and collected 5 spiders and 1 species.  Fifty tapped eastern white pine (Pinus strobus) cones from a stand near the monument parking lot produced 10 spiders and 2 species, plus 11 harvestmen.  The spiders were from the same families I found to be common in eastern white pine cones in Massachusetts, including Salticidae, Thomisidae, Linyphiidae, Phrurolithidae and Dictynidae.

Eastern white pine cones

Bronze cones are spider habitat too!

Amusingly, I even found that a spider had inhabited the sculpted white pine cone at the foot of the monument's statue. 

The Lumberman's Monument statue depicts a river rat, a
timber cruiser and a sawyer but omits the timber baron

Beautiful red pine bark

3-Aug-2015 Green Mountain, Washington

Site locations (click to enlarge)

If ever a mountain lived up to its name, Green Mountain is it.  Emerging from the lowland forest at about 4500 feet (1370 meters) in elevation, hikers on Green Mountain Trail 782 are treated to a spectacular 1.6 mile (2.6 km) wide by half mile high (0.76 km) meadow made green by bracken ferns, at least two species of Rubus, and a variety of flowering herbaceous plants.  Looking southeast across the Siuattle River from the Green Mountain meadows, Washington's most remote volcano, Glacier Peak, is visible shouldering out over Lime Peak.

Small Doug-fir stand in
Green Mtn Pasture

Nobody home

Our first stop of the day was at Green Mountain Pasture at the mountain's base, where I tapped 50 fallen Douglas-fir (Pseudotsuga menziesii) cones from a small stand of trees growing within the pasture.  Although I found an active agelenid web attached to one cone and the occasional spider retreat in others, I found no spiders in the cones.
 

A western white pine cone dwarfs
neighboring Douglas-fir and
western hemlock cones

Its distinctive bark helped me
to locate the parent pine tree

From there a 6 mile drive up the mountainside brought Rod Crawford and me to the Green Mountain trailhead.  Hardly 10 minutes into our hike I spotted a few western white pine (Pinus monticola) cones lying next to the trail and located their source: a single pine tree growing in a forest dominated by western hemlock (Tsuga heterophylla) and Douglas-fir.  But as I've said before, all it takes is one good tree; I had no problem finding 50 fallen pine cones to tap.  From them I collected 12 spiders and 2 species. Two-thirds of the spiders were Cryphoeca exlineae (Hahniidae), a common litter species.  The hemlock cones were so numerous and so much smaller than the pine cones that when I tapped pine cones, a hemlock cone would occasionally fall out.

Green Mountain meadow

A mating pair of grasshoppers

As numerous hikers have noted on the Washington Trails Association's Green Mountain page, the meadow is literally hopping with grasshoppers this time of year.  Each step sets a dozen of them in motion.  Many landed in my net by chance, but never lingered there long enough for me to photograph them.  Only when the air cooled with the setting sun did they slow down enough for portraits.

Pika (Ochotona princeps) on rock

Misumena vatia hunting on
Anaphalis margaritacea

I finally caught up with Rod in a little boulder-strewn draw on the eastern side of the mountain.  He had already sampled conifer litter in a small grove of subalpine trees at its upper end, so I took the opportunity to tap a third set of cones from the same grove.  From 50 tapped mountain hemlock (Tsuga mertensiana) cones I collected exactly zero spiders.  Oh well.  I did enjoy listening to the pikas calling "eep!" while I tapped those empty cones.

Be sure to read Rod's account of the day here!

31-Jul-2015 Mt Ellinor, Washington

Site location map (click to enlarge)

One way to extend the collecting season into the dry summer months is to collect at ever-higher elevations.  This principle led Rod Crawford, Jessi Bishopp and me to Mt. Ellinor, a popular hiking destination on the Olympic peninsula featuring old-growth forest, panoramic views of the Olympics and Cascades, and mountain goats. The peak was named by 19th century geographer George Davidson in honor of his fiancée Ellinor Fauntleroy, later described by their daughter as a woman whose "knowledge of life and the world made her inclusive rather than exclusive -- an universalist in religion and deed".

Mountain hemlock cone microhabitat

Cryphoeca exlineae female in
mountain hemlock cone

Before reaching the trailhead we stopped to collect a lower elevation sample near Skinwood Creek.  I tapped 50 Douglas-fir (Pseudotsuga menziesii) cones that I found lying next to the road and collected 1 spiderling.  Hiking up into the hemlock-fir forest on the Mt. Ellinor trail I tapped a second set of cones, this time from mountain hemlock (Tsuga mertensiana).  Tapping 50 mountain hemlock cones got me 3 spiders and 1 harvestman.  Two of those spiders were female Cryphoeca exlineae (Agelenidae).  I found each in a web located between cone scales.

Boulder talus on upper Mt. Ellinor

Araneus gemmoides

The ascending trail eventually leaves the closed-canopy forest and skirts a boulder talus field before reaching the peak.  Despite the intense heat in the talus field, I found numerous orb-weaver webs strung up between the stones.  From one of these came what for me was the most striking spider of the day, a melanistic Araneus gemmoides (Araneidae) female.  Usually this species is orangish-brown in color.

Mt Rainier viewed from talus
field on Mt Ellinor

The talus field was as high in elevation as I got, but Jessi bounded on up to the summit with her net.  She apparently did some great spider p.r. while up there because numerous descending hikers smiled and asked whether I was collecting spiders too.  Several stopped to talk, including two energetic little boys who wanted to pick up any spiders that I might have in my net.  It was fun to get so many positive responses when "ew!' is the norm.

Goat hair

Everyone I asked had seen mountain goats along the trail, but much to my disappointment I never did.  However, I did find tufts of goat hair stuck here and there to the vegetation.  This helped me spot goat-made game trails that otherwise I probably wouldn't have noticed.

Read Rod's account of the day here!