Eristalis

Eristalis is a genus of hoverflies in the family Syrphidae (Diptera) commonly known as drone flies. The genus includes several species that resemble bees or wasps, a form of Batesian mimicry that helps deter predators. The best-known species is Eristalis tenax, widely distributed and frequently encountered in gardens and wetlands.

Adults are medium-sized hoverflies that visit flowers for nectar and pollen. They are effective pollinators in many ecosystems and can be seen hovering near blossoms or resting on foliage. Their distinctive warning coloration and flight behavior make them familiar to naturalists and gardeners, though identification to species generally requires careful examination or specialist keys.

Larvae of many Eristalis species are rat-tailed maggots, long, slender larval forms with a breathing tube at the posterior end, adapted to aquatic or semi-aquatic environments. They develop in stagnant water, manure, or rich moist substrates where oxygen is available at the water surface. Pupation occurs in soil or mud, and adults emerge after metamorphosis.

Distribution and diversity: Eristalis species are widespread in temperate regions of Europe, Asia, and North America, with some species extending into the tropics. The genus contains many species and is subject to ongoing taxonomic revision; species identification often relies on wing patterns, body markings, and, for some groups, male genitalia.

Ecology and significance: As adults, Eristalis hoverflies contribute to pollination of a broad range of flowering plants. Their larvae perform saprophagous roles in aquatic or damp environments, helping decompose organic matter. They are harmless to humans and are sometimes used in educational demonstrations about insect life cycles and mimicry.