This one I find confusing. It has the wing pattern of a male Common Whitetail (Plathemis lydia) and the body of the female of this species (but not the wing pattern). According to "A Field Guide to the Dragonflies and Damselflies of Massachusetts", Nikula et al, 2nd edition. I finally read some more and discovered that this must be an immature male that has not yet developed the pruinosity of the abdomen that marks the mature male (p.152, 2nd para., Nikula et al).