Thursday, March 12, 2015

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

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