Distribution: The Palaearctic species is distributed throughout Europe, from Scandinavia to North Africa and with an eastward extension through the Middle East, China and Central Siberia (Mohrig 1969, Cranston et al. 1987, Schaffner et al. 2001, Becker et al. 2003).

Habitat: Aquatic stages are primarily found in clear, cold and shady stagnant or slowly flowing, temporary or permanent waters; the breeding sites include ditches, pools, river banks, ponds, garden tanks and rain barrels, in clean, dirty or brackish water (Trpiš 1962, Mohrig 1969, Briegel 1973, Rettich et al. 1978, Cranston et al. 1987, Becker et al. 2003). Due to temperature requirements, larval sites, especially in summer, tend to be heavily shaded with emergent or overhanging vegetation (Cranston et al. 1987). At the southern extremities of its range, in southern Europe and the Middle East, the larvae are rarely found in waters exceeding 20°C and optimum temperatures are considerably lower (Coluzzi 1962, Postiglione et al. 1973). In these regions larvae have been recorded in springs, brooks and cisterns (Schaffner et al. 2001).

Biology: Especially in perennial waters A. claviger shows two (sometimes three) generations per year (Mohrig 1969, Schaffner et al. 2001). According to Becker et al. (2003) females deposit their eggs above the water level into the wet soil. First larval instars appear in spring (April) and due to aquatic conditions larvae may be present throughout the year or disappear when the breeding sites dry-up (Trpiš 1962, Briegel 1973, Rettich et al. 1978, Cranston et al. 1987). A. claviger overwinters exclusively in the larval stage (Mohrig 1969, Briegel 1973, Cranston et al. 1987, Becker et al. 2003). According to Schaffner et al. (2001) larvae are able to survive under ice.

Adults: Adults emerge in early spring (Becker et al. 2003), May or June and are present till late summer or autumn (Trpiš 1962, Mohrig 1969, Rettich et al. 1978, Schaffner et al. 2001). Females feed on a variety of mammals, including humans and are active especially at dusk (Mohrig 1969, Service 1971a, Rettich 1978). They tend to seek the warmth of buildings, particularly animal shelters, early in the year, but rest outdoors when conditions are more clement; biting densities are highest between May and September (Cranston et al. 1987).