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River jewelwing (Calopteryx aequabilis) is a large, 1¼″ to 2⅛″ long, showy, broad-winged damselfly. It is common in northern United States and southern Canada. Males and females are the same size.

The head, thorax, and upper (dorsal) and side (lateral) surfaces of the abdomen of the male are iridescent. The apparent color is determined by the quantity and angle of available light. In good light they appear brilliant metallic green or bright metallic teal blue depending on the angle of the light. In deep shade they appear black. The 8th and 9th abdominal segments have a narrow, white, lateral patch. The lower (ventral) surface of the abdomen is black.

The wings are 1″ to 17 ⁄16″ long and are broad, 3½ to 4 times as long as wide. On mature individuals they are pale smoky brown, almost clear, at the base with a dark brown band at the tip.

After mating the female oviposits eggs inside soft, submerged stems of aquatic plants up to a foot below the surface of the water. Naiads remain in the water for two or three years, molting 12 or 13 times before emerging as an adult. Adults emerge mostly in June. They reach sexual maturity in about 11 days and live on average for 16 to 20 days.