Bicoloured Miner

Appearance

''Andrena bicolor'' is a small to medium-sized mining bee, with the males being slightly smaller than the females. The females have a coat of reddish-brown hairs on the dorsal surface of the thorax, a wholly black-haired face and indistinct bands of yellowish hairs on the margins of the first to third tergites. The spring brood can show an extensive black hair covering on the femur and the sides of the thorax, this is not as marked in the autumn brood. It has dark tibia on the hind legs but these have obvious orange hairs which have been said to resemble a pair of orange leg warmers. The spring brood males have black hairs on the head and side of the thorax and lack the bright colours of the females, while summer brood males often show brown hairs on the face and have no black hairs on the side of the thorax.

Distribution

''Andrena bicolor'' is a widely distributed species in Europe from most of Great Britain and Ireland in the west to southern Fennoscandia south to the Mediterraean, including Corsica, the Balearic Islands, Sicily, Crete and Cyprus but it is not found on Sardinia, its range extends east into Russia and Central Asia. It has also been recorded in Turkey, Israel and Iran. In the Netherlands this species is commoner in the south than in the north but it seems to be expanding its range in the north.

Habitat

''Andrena bicolor'' shows a rather generalist choice of habitat from calcareous grassland to open woodlands, only avoiding closed canopy woodland and high alpine habitats. In some parts of its distribution it can be a coastal species such as in Ireland and parts of Scotland. In the Alps it extends to 1,800 metres in Switzerland but has been recorded up to 2,100 metres in Austria. It has two broods during a season, i.e. it is bivoltine, a spring brood which flies from March to June and a summer brood which flies from June to late August. The first brood is much more numerous than the second brood, and the second brood appears to be much more elusive than the first, especially the males.

''A. bicolor'' is polylectic, meaning that it feeds from a wide variety of flowers. This has been shown by sampling the pollen collected by females. The spring brood has been confirmed as foraging on a wide variety of early flowering plants from low herbaceaous species such as coltsfoot , ''Bellis perennis'', dandelion , buttercups , daffodils and bluebells to spring blossoming shrubs such as hawthorn and willow . However, the summer brood females feed mainly from bell flowers, in particular the harebell and the clustered bellflower as well as such species as white bryony , blackberry , mallows, cranesbills and cinquefoils. In the Ukraine ''A. bicolor'' is regarded as one of the most important pollinators of the cherry crop.

The nest tunnel may be over 1 metre in length and nests can be solitary or in small loose aggregations which are normally on relatively bare ground on south facing banks or slopes. In Germany nests have been found in association with the nests of other ''Andrena'' species such as ''Andrena fulva'' and species of the ''Andrena minutula'' complex. Nests are rarely recorded and are difficult to locate. The cleptoparasitic nomad bee ''Nomada fabriciana'' is associated with ''A. bicolor'' and the fly ''Stylops gwynanae'' may "stylopise" ''A. bicolor'' in Spain and eastern Europe and larval ''Stylops'' have been observed on adult ''A. bicolor''.