There are four genera and 19 species of Emeralds known to occur in Alabama and Mississippi. The nymphs of most of these are found in still or slowly flowing waters, such as manmade or natural ponds, swamps, oxbow lakes, or side channels of streams and rivers. Others, such as the shadowdragon genus Neurocordulia, are specialized to live in flowing water. Still others, such as the genus Somatochlora, may have highly specialized aquatic habitat requirements such as tiny flowing rivulets through a sphagnum bog, or shallow sheet flow across a forested wetland; these nymphs are not often seen. Regardless of habitat, though, many corduliid nymphs are rather uniform in size and features, and can be very difficult to tell apart.