Osmia bicolor (Schrank,1781)

Synonyms

Apis rustica GEOFFROY 1785; Apis fusca CHRIST 1791 (nec. SCOPOLI 1763); Apis fuscescens VILLERS 1789; Apis hirundinaria CHRIST 1791; Osmia pyrenaea LEPELETIER 1841; Osmia fusca GISTEL 1857; Osmia rufitarsis SMITH 1879; Osmia monachiensis STRAND 1917 

Description and notes

The males of this species are among the first of the solitary bees to appear in the spring, with one exceptional record as early as late February. They are shortly followed by the distinctive females.

Video

Male O. bicolor inspecting a snail shell. Female applying spots of chewed up leaves to her nesting shell (possibly to camouflage it) and then bringing in pollen which is attached to special hairs on the underside of her body.
Video by John Walters.

A female Osmia bicolor collecting pieces of grass and dead bramble stems to cover the nest shell in which she had constructed and finished her nest. June 2013.
Video by John Walters

A female Osmia bicolor moving her snail shell nest site in to the optimum position.
Video by John Walters

A female Osmia bicolor finishing off covering her snail shell nest with 30 more pieces of grass in half an hour of warm sunshine.
Video by John Walters

A female Osmia bicolor searching for, picking up and carrying "sticks" back to its nest. Video by Martin Harvey - 17 May 2015.

Distribution

Distributed predominantly in southern England and south Wales, the range being closely correlated with chalk and limestone soils. This is a predominantly central European species, becoming rare and sporadic north of Belgium. The Palaearctic range extends from southern Finland (one record only (Elfving, 1968)) to Spain, and east to the former Yugoslavia and Romania. Stoeckhert (1933) records the species from central Asia and reports that both there and in southern Europe it is largely restricted to montane sites.

Status (in Britain only)

Classified as a Nationally Notable (Nb) species by Falk (1991).

Habitat

Generally calcareous grassland and open deciduous woodland on chalk and limestone soils.

Flight period

Univoltine; April to early July. The males are very short-lived in comparison with the females.

Pollen collected

Polylectic, visiting species in the families Primulaceae, Rosaceae, Lamiaceae, Asteraceae and Liliaceae.

Nesting biology

Females establish their nests in empty snail shells, including those of Helix pomatia, Cepaea nemoralis, C. hortensis and Monacha cantiana. Nests contain about four or five cells, depending on the size of shell used. Cell partitions and the closing plug consist of leaf mastic (i.e. masticated portions of green leaf). The space between the last cell partition and the closing plug is filled with a rubble containing very small snail shells and pieces of chalk, or soil. When the nest is completed the female covers the shell with a mound of dead grass stems, beech scales or leaf fragments (Perkins, 1884, 1891; G R Else, pers. obs.). The reason for this behaviour is not known, but it may camouflage the nest from possible parasites and predators at a time when it may be vulnerable to such attack. Nests are illustrated by Geiser (1988) and Westrich (1989). Males have been found sheltering in empty snail shells during periods of inclement weather (G R Else, pers. obs.).

Flowers visited

Wood anemone (Anemone nemorosa), bluebell (Hyacinthoides non-scripta), heath dog-violet (Viola canina), bird's-foot-trefoil (Lotus corniculatus), horseshoe vetch (Hippocrepis comosa), sainfoin (Onobrychis viciifolia), sallow (Salix spp.), ground-ivy (Glechoma hederacea), daisy (Bellis perennis) and dandelion (Taraxacum sp.).

Parasites

No information available.

Author of profile

G R Else.

Year profile last updated

Profile written: 1998

Proofed: February 2012