The Nannochoristidae are a primitive family of scorpionflies with many unusual traits. It is a tiny, relict family of about eight species, with members of the genus Nannochorista occurring in New Zealand, southeastern Australia, Tasmania, and Chile, so is probably of Gondwanan origin. The adults look like scorpionflies with more pointed, elongated wings. Most mecopteran larvae are eruciform, or shaped like caterpillars. Nannochoristid larvae, however, are elateriform, or shaped like wireworm or click beetle larvae. They are also the only entirely aquatic Mecoptera. Wing venation suggests a close relationship to dipterans. They are predatory, primarily on the larvae of aquatic Diptera.
Some research suggests the nannochoristids are the only holometabolous insects with true larval compound eyes . All other eyed larvae have stemmata, which are structurally different from adult compound eyes with ommatidia. This is unusual, since most adult features are present as imaginal discs in larvae and not formed until pupation. The presence of compound eyes in nannochoristid larvae suggests the timing of the development of adult features can be initiated earlier in development, which has important implications for insect evolutionary development.