Ephydra hians, commonly known as the alkali fly or Mono Lake fly, is a species of brine fly in the family Ephydridae that is endemic to the highly alkaline, hypersaline environments of the western United States, most notably Mono Lake in California. The genus name Ephydra is derived from the Greek ephydros, meaning "living in or near water," while the species epithet hians is Latin for "gaping," a reference to the fly's distinct morphological features. Historically, this insect has been a critical keystone species within its arid-land ecosystem, serving as the primary bridge between primary productivity (algae) and the upper trophic levels, supporting millions of migratory birds that flock to the lake annually.

The fly is famously adapted to extreme environments where few other multicellular organisms can survive. Its life cycle is largely aquatic, consisting of egg, larval, and pupal stages that occur entirely underwater. Adult flies have evolved unique physiological adaptations to cope with the lake's caustic, high-pH waters, including a dense coat of fine, hydrophobic hairs that trap a protective air bubble against their bodies when they dive. This "scuba" mechanism allows them to graze on benthic algae and lay eggs on submerged substrates for up to 15 minutes at a time. After metamorphosis, the pupae float to the surface to emerge as winged adults, which then congregate in massive, carpet-like clouds along the lake's shoreline, providing a high-protein resource for predators.

Ephydra hians—specifically its pupae—has been an essential nutritional pillar for indigenous populations, most notably the Kutzadika’a (Mono Lake Paiute) tribe, who referred to the harvested pupae as kootzabe (or koo-tsabe). Historically, the Kutzadika’a harvested the pupae in vast quantities by scooping them from the shallows or gathering those washed onto the shore by waves. Once collected, the pupae were cleaned, sun-dried, and subsequently ground or cooked into nutrient-dense stews and porridges. The resulting product is characterized by a high concentration of essential fats and proteins, serving as a vital calorie-dense staple during the winter months. In the modern era, while the fly remains ecologically paramount, its direct consumption by humans is limited to niche historical and cultural contexts, though it is increasingly studied in the broader scientific investigation of edible insect proteins and sustainable food systems.

Nutritionally, the alkali fly is a robust source of protein and essential lipids, containing a highly favorable amino acid profile that can rival conventional meat sources. Mature larvae and early pupae are particularly high in caloric density, containing approximately 11–12 calories per individual, which explains their importance as a "fuel" for migratory birds like phalaropes, which often double their body weight after feeding on the flies. Because the larvae and pupae develop in a high-salinity environment, they also possess a distinct mineral profile, including elevated levels of sodium and carbonate-derived compounds. Modern research into the fly's potential as a functional food focuses on its high digestibility and the bio-availability of its nutrients, though harvesting must be carefully managed to maintain the delicate ecological balance of the fragile saline lakes they inhabit.