Sunday, March 8, 2015

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
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

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