An odonatan is any member of Odonata, an order of primitive winged insects found worldwide. Damselflies, in the suborder Zygoptera, have thin bodies with wings held vertically along the body when at rest. The long, slender, aquatic nymphs have three, leaf-like gills on the abdomen. Dragonflies, in the suborder Anisoptera, have heavy bodies with wings held horizontally when at rest. The stout nymphs have gills at the anal end. All prey on insects; none attack humans. Length: 18–193 millimeters (0.7–8 inches).