Nannochoristidae is a family of scorpionflies with many unusual traits. It is a tiny, relict family with a single extant genus, Nannochorista, with eight species occurring in New Zealand, southeastern Australia, Tasmania, Argentina and Chile. Due to the group's distinctiveness from other scorpionflies, it is sometimes placed in its own order, the Nannomecoptera. Some studies have placed them as the closest living relatives of fleas. Most mecopteran larvae are eruciform, or shaped like caterpillars. Nannochoristid larvae, however, are elateriform, and have elongated and slender bodies. The larvae are aquatic, which is unique among mecopterans. The larvae are predatory, hunting on the beds of shallow streams, primarily on the larvae of aquatic Diptera like chironomids. The adults are thought probably to be adapted to liquid feeding, likely on flower nectar and/or the juice of fruits. Adults of Australian and South American species are often found in habitats like the edges of streams, lakes, as well as montane bogs. Australian species have been observed visiting the foliage and flowers of Leptospermum (tea trees).
Fossils indicate that Nannochoristidae formerly had a wider distribution, being present in the Northern Hemisphere during the Jurassic and Early Cretaceous.
