Not a damselfly but a dragonfly, a Ruddy Darter, Sympetrum sanguineum, which is probably mating.
Picture taken by the pond September 3.
Thanks for the identification to @peediepuss https://twitter.com/peediepuss/status/377527457127350272 and @grumpy_toad https://twitter.com/grumpy_toad/status/377487251749756928 .