Hot Off The Press: A Survey Of Spiders Found In Fallen Pine Cones In Eastern Washington State

Our pine cone spider paper is out!  "A survey of spiders found in fallen pine cones in eastern Washington State", written by me and Rod Crawford, has just been published in Vol. 74, No. 4 (2014) of Western North American Naturalist.  Download the .pdf here.

To get you started, here is the abstract in English and Spanish:

A survey of spiders found in fallen pine cones in eastern Washington State

Laurel J. Ramseyer, Rodney L. Crawford

Abstract

Fallen pine cones are a microhabitat for spiders in Washington State. Eighty-nine species of spiders from 24 families and 70 genera were identified from 1060 specimens collected from over 4567 cones of Pinus ponderosa and Pinus monticola between 2008 and 2013. Euryopis formosa Banks 1908 (Theridiidae) and Pholcophora americana Banks 1896 (Pholcidae) were the most abundant species collected (27% and 9.3% of identified specimens, respectively) and occurred most frequently (49% and 21% of sampling sites, respectively). Fallen cones may be an important microhabitat for these species in Washington. Fallen cones produced 18 spider species rare in Washington, including Theridion rabuni Chamberlin and Ivie 1944 (Theridiidae), which has not been found in any other microhabitat in the state. Sampling fallen cones added a mean of 3 species (SD 2, range 0–9) to site lists created by conventional collecting methods like sweeps, litter sifting, and foliage beats. Agelenid spiders incorporated entire cones into their webs, while other species placed egg sacs or retreats on cone surfaces or used the inner spaces of cones to build prey capture webs or to molt.

Encontramos que las piñas caídas son un microhábitat para las arañas en el estado de Washington. Se identificaron 89 especies de arañas de 24 familias y 70 géneros en 1,060 muestras obtenidas de más de 4,567 piñas de Pinus ponderosa y Pinus monticola entre los años 2008 y 2013. Las especies colectadas más abundantes fueron Euryopis formosa Banks 1908 (Theridiidae) y Pholcophora americana Banks 1896 (Pholcidae), (27% y 9.3% de las muestras identificadas, respectivamente) y encontradas con mayor frecuencia (49% y 21% de los sitios de muestreo, respectivamente); las piñas caídas podrían representar un microhábitat importante para estas especies en Washington. Las piñas caídas mostraron 18 especies de arañas poco comunes en Washington, incluyendo Theridion rabuni Chamberlin e Ivie 1944 (Theridiidae), que no se ha encontrado en ningún otro microhábitat en el estado. La toma de muestras de piñas caídas añadió un promedio de 3 (DE 2, entre 0 y 9) de especies a las listas de sitios creadas por los métodos convencionales de recolección tales como redadas, tamizado de arena y golpeo de follaje. Las arañas Agelenid incorporaron piñas enteras en sus telarañas, mientras que otras especies colocaron sacos de huevos o crearon lugares de retiro en las superficies o utilizaron los espacios internos de las piñas para construir redes para capturar presas o para mudar de piel.

13-Oct-2012 Wachusett Reservoir Gate 33, Massachusetts

Site location (click to enlarge)

Pine amid glowing maples

My 25th and final Wachusett Reservoir cone sampling site was a stony beach running along the southeastern shore of Greenhalge Point. By this time of year the maple trees were reaching peak autumn color, making the mile-long hike to the shore a glorious experience. Although Greenhalge Point is a popular destination for fishers (check out the Wachusett Reservoir Fishing Addicts page on Facebook, for example), I again had the place all to myself this day.  Throughout the summer the Wachusett Reservoir had been a quiet, peaceful place where I seldom encountered others beyond the parking areas.

Sample site

Lots of open cones ready to fall

Fallen cone on the rocky shore

Eastern white pine (Pinus strobus) trees growing at the forest edge had dropped open cones on the shore below.  Tapping 50 cones I collected 10 spiders, all juveniles.  Among them was a Euryopis sp. (Theridiidae).  Although I had collected two other juvenile Euryopis sp. from cones back in late July, there doesn't appear to be any species of Euryopis that is a reliable denizen of fallen cones in central Massachusetts like E. formosa is in eastern Washington state.

I didn't sift any litter at this site since I found almost none associated with the cones that I sampled.  And while the content of this final cone sample wasn't particularly exciting, it was gratifying to know that it contributed to the overall picture of spiders in fallen pine cones at Wachusett Reservoir. Over the course of my Wachusett Reservoir survey I tapped 338 spiders from 1,389 fallen P. strobus cones and sifted 331 spiders from about 115 liters of associated litter. Although many specimens still await complete identification, I collected about 30 morphospecies from fallen cones at Wachusett Reservoir.

6-Oct-2012 Wachusett Reservoir Gate 19, Massachusetts

Sample location

My penultimate Wachusett Reservoir sampling day brought me back to the south end of the reservoir.  A short walk through an oak-maple (Quercus - Acer) forest brought me to a row of eastern white pine (Pinus strobus) growing behind the arborvitae (Thuja occidentalis) curtain that parallels the shore.

Sample site

The fallen cone & litter microhabitats

Tapping 50 cones I recovered 21 spiders.  Similar to the cone samples at the previous two sites, this one had a higher than average number of spiders per cone relative to my other Wachusett Reservoir sites.  Most of the specimens were juvenile phrurolithids, linyphiids and thomisids, but a female Lathys pallida (Dictynidae) and a female microspider that I've collected numerous times but haven't yet identified gave me a species count of 2.

Ladyparts of a Ceraticelus minutus

My litter sifting gear

The litter, which was composed of pine needles and deciduous tree leaves, contained quite a variety of mature linyphiid microspiders.  I counted at least 6 morphospecies.  The only one I could immediately identify was Ceraticelus minutus (Linyphiidae). Present also were mature Hahnia cinerea (Hahniidae), a male agelenid (11 mm long!) and numerous juvenile phrurolithids and thomisids.

Coral-shaped fungus

A fungus amongus

An amazing array of fungi were growing at this collecting site: puffballs, purple-capped mushrooms, coral-shaped fungus, white, flat-topped mushrooms big as my palm pushing up through the litter, and more.

First touches of fall color

This no-parking area monitored by bluebirds.

12-Sep-2012 Wachusett Reservoir Gate 9, Massachusetts

Site location

The forest west of newly-constructed Tahanto Regional Middle/High School was the day's destination.  Huge earth-moving machines were making a racket in the school's parking lot, but the construction noise faded as I made my way deeper into the woods.

Trail through collecting site

Eastern white pine (Pinus strobus) dominated the overstory at my collection site and blanketed the trail and forest floor with needles.  The understory was dense with red maple (Acer rubrum) saplings, while blueberry (Vaccinium sp.) was a significant element in the ground layer.

Fallen cones under Vaccinium sp.

Mystery spider from cones

As in the previous week, I again got 22 spiders from 50 tapped cones, making this one of the most productive cone sites around the reservoir.  However, the composition of this sample was different.  Almost half of the specimens were of a species of microspider I hadn't seen before and haven't yet identified.  The rest were mainly the usual suspects: dictynids, gnaphosids, phrurolithids and thomisids.

A snouty Ceraticelus male

Mystery spider's epigynum & abdomen

The pine needle litter was also abounding with spiders.  I sifted 32 individuals and 8 species, including a few penultimate male specimens of the "mystery spider" I found in the cones.  Lathys pallida (Dictynidae) was the most numerous identifiable species present (3 females & 3 males), while 4 female Hahnia cinerea (Hahniidae) made that species the second-most common.  So much for my previous comment about collecting one and only one hahniid per sampling site!

Just someone I met on the trail...

3-Sep-2012 Wachusett Reservoir Gate NoNumber, Massachusetts

Site location

Thus far my collecting days at Wachusett Reservoir had been solitary affairs, but this time I had company!  September 3 being Labor Day, my wife Marie Rose had the day off and was eager to explore the reservoir shoreline while I collected my weekly cone and litter samples.

L to R: oaks, pines, arborvitae, reservoir

We accessed the collection site by way of an unnumbered gate located immediately south of Gate 22.  A short hike through an oak (Quercus sp.) forest brought us to a small bluff overlooking the reservoir.  A few feet before the bluff fell to the shore, the oaks gave way to a strip of eastern white pine (Pinus strobus) and then a curtain of arborvitae (Thuja occidentalis), both growing parallel to the shore.  Regular readers of this blog will already know that this is a very common configuration around the reservoir, a legacy of the extensive reforestation effort that began over 100 years ago after dam and reservoir construction were completed.

Pine cones and litter

Me sorting my tapping sample

Tapping 50 cones, I got a whopping 22 spiders.  This translates to 0.44 spiders per cone, almost twice the average for Wachusett Reservoir cones and a density equaled at two other reservoir sites but never surpassed.

Micaria sp.

Of those 22 spiders, only two were mature: a female Lathys pallida (Dictynidae) and a female Eridantes erigonoides (Linyphiidae).  I'd collected one specimen of each only once previously, those being from cones tapped in August.  I also tapped my first ant mimic Micaria sp. (Gnaphosidae) from these cones.  I'd collected two others earlier in the summer, but those were from litter.

Epigynum of Ceratinella brunnea

The litter contained 3 or 4 species from 8 families, including a female microspider Ceratinella brunnea (Linyphiidae).  Out of the 23 specimens I collected from litter, 6 were juvenile Phrurotimpus sp. (Phrurolothidae), 3 were dictynids and another 3 were thomisids.  Most of the remainder were microspiders TBD, but I also collected a male Hahnia cinerea (Hahniidae).  I've collected one (and only one!) hahniid at half of my Wachusett Reservoir sampling sites, sometimes from cones, sometimes from litter.

Misumenoides formosipes waiting to embrace her next meal.

On her hike along the shore, Marie Rose spotted what on first glance appeared to be my old friend Misumena vatia (Thomisidae), the species of crab spider that drew me into arachnology.  But inspection under the dissecting scope revealed that the true identity of this living lemon drop was Misumenoides formosipes (Thomisidae).  The two species look amazingly similar to the naked eye, but besides having slightly different epigynae, they differ in another feature which can actually be seen on a good digital image of a living animal: M. formosipes has a "white clypeal carina", a white line running more or less horizontally across the "face" under the eyes (see Fig. 416 on p. 125 in Dondale & Redner).  Now that I know what to look for, I can see the carina in some of my photos from the day.

Smartweed (Polygonum sp.) in the forest's afternoon shadow

27-Aug-2012 Wachusett Reservoir Gate 35, Massachusetts

Site Location

This pine cone spider collection site was about 0.25 to 0.5 miles further down the Gate 35 trail than were my very first sample sites at Wachusett Reservoir. That short distance brought me to an entirely different topography from the former up-trail sites: a rocky bluff overlooking Prescott Cove.

Loon on the reservoir

The day began on a serious note when I read a "missing" notice about a local and much-loved young man posted at the gate.  An MWRA ranger had given me a flier about him the month before, and asked me to be on the lookout for him.  Sadly, his body was eventually found in the woods south of the reservoir, an apparent death by suicide.  After pondering the still-missing man during my hike in, I was happy to have the lively company of this loon.

View from atop the rocky bluff

My cone source was a stand of eastern white pines (Pinus strobus) and oaks (Quercus sp.) on the bluff top.  I found about half of the cones I sampled lying on reindeer lichens (Cladonia sp.) on the face of the bluff, while the rest came from the edge of the forest floor near the bluff face.

Cone on lichen on rock

I collected 11 spiders from 50 tapped cones but only one specimen was mature, a female Lathys pallida (Dictynidae).  The rest were from families I've found to be common in Wachusett Reservoir cones: Gnaphosidae, Lycosidae, Phrurolithidae, Salticidae, and Thomisidae.

I also found a lycosid exuvium in the cones.  The family's distinct eye pattern and notched trochanters make their exuviae the easiest for me to recognize.

Cone on forest litter

The pine needle & oak leaf litter was very thin and dry, yet still produced 15 juvenile spiders.  These included numerous gnaphosids of several genera as well as five Titanoeca sp. (Titanoecidae).

Micrathena gracilis out of web

Perhaps the most conspicuous animal in the forest this day was the orb-weaver Micrathena gracilis (Araneidae).  The females of this species build large, foot-wide orb-webs and wait smack in the middle. 

Micrathena gracilis in web

When a ray of sun streams through the canopy and hits her dense web and white, ten-spined dorsum, she blazes like a star.  It's quite a sight to see.

Acorn and mushroom

20-Aug-2012 Wachusett Reservoir Gate 8, Massachusetts

Site location

Back again to Sawyers Bluff, this time to the forest-backed cove on the northwest side.

Southward view of bluffs

My view to the south was the bluffs.  To the north I could see the sandy point that sticks out into The Narrows, a popular destination for hikers.

Northward view towards point

The forest edge, where my cones originated, was composed largely of eastern white pine (Pinus strobus) and oaks (Quercus sp.), with small amounts of aspen and birch growing on the forest edge and the beach itself.

Cone on pine needles and sand

The pine cones I tapped here were lying variously on bare sand, pebbles and cobbles, or very thin needle and leaf litter over sand. From 50 cones I collected one mature harvestman and 17 juvenile spiders from the families Dictynidae, Gnaphosidae, Hahniidae, Linyphiidae and Salticidae.

Could be a juvenile Cesonia bilineata

Cone with spider egg sacs

Since all of my spider specimes were juveniles, I couldn't confidently identify any of them to species.  However, I did tentatively identify four specimens as Cesonia bilineata (Gnaphosidae), based on description of their eye arrangement and unique coloration by Kaston (1981).  Platnick and Dondale (1992) reported that the species has been collected on sand dunes as well other habitats, so that also tracks.

I didn't sample litter at this site since there was hardly a handful present.

Nice view

16-Aug-2012 Wachusett Reservoir Dam, Massachusetts

Location of Wachusett Reservoir dam

Wachusett Dam face & lower gatehouse

For months I'd seen the Wachusett Reservoir dam in the distance, but never had the opportunity to stop and take a closer look.  This would be the day!

Lower dam face

Wasp taking a sip

The dam face and lower gatehouse are composed of ashlar-cut granite that was quarried in nearby Chelmsford, Massachusetts.  I found the dam face busy with life, including a male jumping spider Sitticus pubescens (Salticidae) hunting on the dry stones while a wasp appeared to be drinking from a seep just a few inches away.

Female Pardosa milvina

Male Pardosa milvina

Mature wolf spiders Pardosa milvina (Lycosidae) were dashing so quickly across the wet lower face of the dam that I had difficulty photographing them.  The species "appear to reach high numbers in moist habitats such as swamps, meadows, mud flats, and the edges of ponds and creeks" according to Dondale and Redner (1990).  That certainly was the case here wherever marshy lawn abutted the dam!

Female Agelenopsis potteri

Jump!

The outer surfaces of the gatehouse furnished numerous niches for spiders and other invertebrates.  A female funnel weaver Agelenopsis potteri (Agelenidae) had taken up residence on a window sill, while numerous female Parasteatoda tepidariorum (Theridiidae) hung their distinctive egg sacs in the corners of doorways.  Salticids roamed the granite surfaces, and wasps built their mud nests in decorative recesses between stones.

Gatehouse gone condo

The A. potteri that I collected from the gatehouse was so big that I couldn't get her into my wet vial and had to improvise with a small plastic bag.  Many of the spiders I collected here at the dam were so much larger than I was accustomed to finding in fallen pine cones in the woods around the reservoir.  Could this be because larger spiders are unable to fit between the scales of the fallen cones I've sampled in the area?

Centenarian hawthorn (Crataegus sp.) trees still thriving in front of gatehouse