Comparison of second abdominal segment in male blue damselflies

Common blue damselfly Enallagma cyathigerum round marking joined to black ring at posterior edge of segment	Irish damselfly Coenagrion lunulatum crescent or boomerang-shaped marking not joined to other black markings	Azure damselfly Coenagrion puella U-shaped marking not joined to black ring at posterior edge of segment	Variable damselfly Coenagrion pulchellum U-shaped marking joined to black ring at posterior edge of segment to make wineglass shape