Most of the clubtails are medium in size with black and yellow coloration and variously-sized "clubs" at the end of their abdomen. They are unique in that their eyes do not meet on top of their head. Not surprisingly, identification clues lay largely in the size and patterns of the club, but clasper shape, shape of the abdominal top spots, pattens of the thoracic side and top stripes, and absence/presence of black on the face are also important in various cases. Most species, including the green-thoraxed "snaketails," require clean, fast-flowing rivers and streams with high oxygen content and are active in early to mid-summer. I stumbled upon 13 species in 2008.