Distribution: The species is confined to the northern parts of the Holarctic regions; the circumpolar distribution area extends from Central and Northern Europe, throughout Siberia to North America (Mohrig 1969, Schaffner et al. 2001, Becker et al. 2003).

Habitat: Aquatic stages live in temporary or semi-permanent water bodies, in peat bogs, forest ponds and ditches, sometimes in open marshes and rock pools (Peus 1929, Peus 1939, Schaffner et al. 2001, Becker et al. 2003). Mohrig (1969) notes that O. diantaeus is typical for moors. Rettich et al. (1978) found larvae in periodic breeding places at the border of a deciduous forest. Wood et al. (1979) suggest that the long antennae of the larval stages may indicate a peculiar feeding behaviour.

Biology: The species is monocyclic; larvae appear in mid or late spring (Mohrig 1969), stemmed from overwintering eggs (Schaffner et al. 2001). Adults emerge from May onwards to July and are present during the summer months (Mohrig 1969, Rettich et al. 1978, Schaffner et al. 2001).

Adults: Females feed on mammals, including man, mainly at dusk and down (Mohrig 1969). Transmissions of parasitic diseases to humans are not known at present (Schaffner et al. 2001).