Adults are slender, soft-bodied, with four membranous, extensively veined wings held upright and together (like a butterfly). The forewings are much longer and often overlap the hindwings. When perching, the front pair of legs are often held outward. They have short antennae and large compound eyes. There are 2 long, threadlike cerci (antenna-like appendages extending from the tip of the abdomen). The naiads (nymphs) somewhat resemble the adults, though they lack wings, have a series of leaflike external gills attached below the abdomen, have smaller eyes and often have a flattened head that helps them to adhere to rocks in fast-flowing water. Nymphs possess 3 long cerci (sometimes 2) extending from the tip of the abdomen.