For about an hour one recent, hot afternoon in the farmland of eastern Lancaster County, Pennsylvania, I was driving around a bit to see what was new in nature. I didn't see much wildlife until I came to a clear, cold brook running through a grove of planted willow trees, and closely paralleling a rural road. Because that stretch of road was shaded and relatively cool, I stopped to see what wildlife was in that brook, and the ground, trees and jewelweeds around it.
Immediately, I saw more male black-winged damselflies in that 50-yard stretch of waterway than I have ever seen in other brooks of that size. Some metallic-green, male damselflies with four black wings were fluttering together daintily, like pretty butterflies in sunbeams, above the shallow waterway, creating a beautiful, entertaining sight. Their "dancing" was their attempts at intimidating each other away from a prime breeding site, and to attract females to the winners for mating. I was taken with their bold iridescence in slanting shafts of sunlight that penetrated the shadows.
Southeastern Pennsylvania has two common kinds of damselflies, that are striking in appearance, but overlooked by most people- black-winged and bluet. Black-wings of the broad-winged damselfly family and bluets of the narrow-winged damselflies are as lovely around clear, running water as any bird or flower is on land.
Male black-wings have iridescent-green, or blue, bodies and four black wings they hold upright over their bodies when at rest. Their females are brownish all over, which allows them to blend into their surroundings. Male bluets are blue with black rings on their abdomens and four clear wings that are held above their bodies. Their mates are similar, but paler.
Related to dragonflies, these two families of damselflies, and dragonflies, have characteristics in common. Dragonflies and damselflies start life as wingless nymphs, larvae, in water. All those nymphs eat tiny, aquatic invertebrates they find in mud or under stones.
Nymphs of both families of damselflies have feathery-looking gills poking from the ends of their abdomens. And they are all the color of mud and stones, which blends them into their niches, the black-wing larvae among stones in small waterways and the bluet young in the mud of ponds.
Adults of both families of damselflies have narrow abdomens, to the point that they are almost hard to see. Adults of both groups consume aphids and other kinds of small, soft-bodied insects on plants and in the air. And damselflies are part of food chains because preying mantises, spiders and several kinds of birds eat them.
But the two-inch-long black-winged damselflies and the one-inch-long bluet damselflies also have differences. Black-winged females spawn eggs in the tissues of plants in the slow shallows of brooks and streams in tree-shaded habitats. Bluet females, however, place their eggs on mats of alga, or other vegetation, in sun-warmed, still ponds. These damselfly species reduce competition for living space and food with each other by being adapted to different niches. And being adapted to different niches created each kind of damselfly.
Interestingly, male black-winged damselflies repeatedly open their black wings slowly, then snap them shut when they are perched on brookside vegetation. This probably is a communication to female black-wings that they are present and available for mating.
The attractive bluet damselflies are also entertaining to watch, but in different ways than the black-wings. Bluets often form groups on floating mats of alga and other aquatic plants where they mate and lay eggs on the wet vegetation. They also dart about, often in pairs, over the water when chasing each other or potential prey. But bluets are so thin they are often difficult to see over or on the sky-reflecting waters' surfaces. One has to look closely to spot them.
Look for these two kinds of damselflies in appropriate habitats. Though unknown insects, they are big in beauty and intrigue.
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