The Ebony Jewelwing (Calopteryx maculata) is doubtless the most easily identified damselfly in the Eastern U.S.. It's large size (1 3/4 inches) and distinctive black wings make it easy to spot and observe. The abdomen of the male is a brilliant metallic green, but often (as in these photos) appears blue.
Females are duller and a bit smaller, with a white patch on the wing tip (pterostigma).
Males engage in "flights of attrition" in battles over territory and mates by flying closely around each other until one tires and either leaves or lands. Above shows another interesting behavior (by both sexes). "Wing clapping." While at rest, the wings are slowly opened...then suddenly and quickly closed.
Ebony Jewelwing habitat is woodland streams and they seem to prefer open areas with rapidly moving water and nearby trees for night roosting. Their distribution is all over the Eastern U.S. west to Kansas and Oklahoma.
Females will oviposit 7-10 eggs a minute in rotten and submerged vegetation. They can lay 1800 eggs lifetime. Longevity is only 2-3 weeks and flight season here in Maine is from June through September (lest we get snow on Labor Day!!!).
Dragonflies and Damselflies are fascinating. The Princeton Guide, by Dennis Paulson is wonderful....get one on Amazon!