Distribution: Ae. geminus is supposed to be mainly distributed in Central and Western Europe (Peus, 1972). The distribution stays poorly known because a large number of records of Ae. cinereus actually must correspond to this species (Schaffner et al. 2001, Becker et al. 2003).

Habitat: According to Schaffner et al. (2001) it is a typical flood-plain species; breeding sites were located in areas liable to be flooded with fresh waters, like prairies and flooded forests; ground and arborescent vegetation is often abundant. In Austria larvae were found in May in shallow temporary stagnant waters in peat bogs, near the border to Czechia, associated with Cs. morsitans, O. communis, O. diantaeus and O. punctor.

Biology: The species is polycyclic, showing at least two generations (Schaffner et al. 2001, Becker et al. 2003). After hibernation in the egg-stage, first larvae hatch in spring after snowmelt; hatchings follow one another until the end of summer; adults are found up to the first frosts (Schaffner et al. 2001).

Adults: Females are aggressive toward humans; they can fly far from their breeding sites and may cause a strong nuisance (Schaffner et al. 2001, Becker et al. 2003). The medical importance is unknown (Schaffner et al. 2001).