ADULTS: The most reliable way to distinguish a dragonfly (sub-order Anisoptera) from a damselfly (sub-order Zygoptera) is based on the wing venation. However, as a rough guide, dragonflies tend to be heavier-bodied that damselflies, and they tend to rest with their wings held horizontally. Their compound eyes tend to join in the middle, whereas they are widely separated in damselflies.
LARVAE: The larvae of nearly all species are aquatic, with just a few tropical species found in moist leaf litter. Dragonfly larvae are stout-bodied and lack the terminal gills of damselfly larvae. Many larvae are readily identifiable to family. To identify a larva to genus or species usually requires microscopic examination.