If you go for a walk near almost any wooded stream in the eastern U.S. or Canada this time of year, especially in the early afternoon, you’ll probably see this damselfly — the ebony jewelwing, Calopteryx maculata. Its aquatic larvae live in or behind debris dams in smaller streams, which I guess would tend to make them more numerous in older forests with more coarse woody debris. The adult males are easy to identify with their metallic blue or green abdomens, and the females are even more distinctive with the white spots, or stigmas, on the ends of their wings.
The males battle each other for territory, aeriel duels that might be more spectacular if they weren’t such weak flyers. However, this latter feature makes for extremely cooperative photographic subjects: males and females spend many long seconds at a time resting on sunlit leaves. Females are relatively more sedentary than males, who not only try to keep other males out of their territory, but engage in what’s called mate-guarding at the same time. Biologists who have studied C. maculata have concluded that the main function of the stigmas is to make the females easier for the males to keep track of.