''Osmia bicolor'', the two-coloured mason-bee, is a
Palearctic
The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa.
Th ...
species of
bee
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamil ...
in the genus ''
Osmia
Mason bee is a name now commonly used for species of bees in the genus ''Osmia'', of the family Megachilidae. Mason bees are named for their habit of using mud or other "masonry" products in constructing their nests, which are made in naturally o ...
''. It is outstanding amongst other megachilid bees in that it nests in empty snail shells.
Description

''Osmia bicolor'' females are small bees, 12 mm in length, with a black head and thorax and an abdomen covered in bright ginger hair. In the males the ginger colour of the abdomen is less intense.
Distribution and habitat
''Osmia bicolor'' is found in Europe and western Asia from southern Great Britain in the west east to
Turkestan
Turkestan,; ; ; ; also spelled Turkistan, is a historical region in Central Asia corresponding to the regions of Transoxiana and East Turkestan (Xinjiang). The region is located in the northwest of modern day China and to the northwest of its ...
, it is found as far north as southern Scandinavia and Finland, and south as far as
Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
and
Romania
Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
.
[ It occurs in grasslands and open deciduous woodland over calcareous soils underlain by rocks such as limestone and chalk.][
]
Biology
''Osmia bicolor'' is univoltine
Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is most often applied to insects, and is particularly in use in sericulture, where silkworm varieties vary in their voltinism.
...
in western Europe and is among the first bees to emerge in the spring, males can be seen as early as February, although the normal flight period is from April to July. The females emerge a few weeks after the males and are quickly mated. Compared to females the males have a very short life.[ Once mated the female ''O. bicolor'' seeks out the empty shells of snails, In Britain it has been recorded using the shells of '']Helix pomatia
''Helix pomatia'', known as the Roman snail, Burgundy snail, or escargot, is a species of large, air-breathing stylommatophoran land Snails, snail native to Europe. It is characterized by a globular brown shell. It is an edible species which comm ...
'', ''Cepaea nemoralis
The grove snail, brown-lipped snail or lemon snail (''Cepaea nemoralis'') is a species of air-breathing land snail, a terrestrial molluscs, terrestrial pulmonate gastropod mollusc.
It is one of the most common large species of land snail in Euro ...
'', ''Cepaea hortensis
The white-lipped snail or garden banded snail, scientific name ''Cepaea hortensis'', is a large species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Helicidae. The only other species in the genus is ''Cepae ...
'' and ''Monacha cantiana
''Monacha cantiana'', common name the "Kentish snail" or "Kentish garden snail", is a species of medium-sized air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
Dist ...
''.[ While in Europe it has also been recorded using the shells of species in the genera '' Arianta'', '']Crepidula
''Crepidula'', commonly known as the slipper snails, slipper limpets, or slipper shells, is a genus of sea snails, marine (ocean), marine gastropod mollusks in the family Calyptraeidae. This family includes the slipper snails (''Crepidula''), hat ...
'', '' Fruticicola'' and ''Helicella
''Helicella'' is a genus of small to medium-sized, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the subfamily Helicellinae of the family Geomitridae, the hairy snails and their allies.MolluscaBase eds. (2021). Mollusca ...
''. Once the female has selected a shell she moves into her preferred position before depositing balls consisting of chewed up masticated pollen and nectar to provision the nest. One egg is laid on each ball and the female then builds a cell around the egg and food provision.[
]
Depending on the size of the shell there will be four to five cells per shell and the shell will be sealed with the same type of chewed up leaf material, leaf mastic, as used to create the cells, as well as being speckled on the outside of the shell as camouflage.[ The female will also deposit sand, gravel and soil between the last cell and the plug as an anti-predator barrier. The shell is then manipulated by the female so that the entrance is facing towards the ground.][ Once the nest is complete the female covers the shell in a canopy of grass stems, small twigs or leaves to camouflage it.][ She uses her saliva to bind the canopy materials together. The females are often seen carrying these materials which can be many times the length of the bee.][ If the soil is soft enough the female may also partially bury the shell.][ Male ''O bicolor'' have been recorded using empty snail shells as shelters during periods of cold or wet weather and at night.][ The female will make up to six or seven nests in the breeding season.][ The ]cuckoo wasp
Commonly known as cuckoo wasps or emerald wasps, the hymenopteran family Chrysididae is a very large cosmopolitan group (over 3000 described species) of parasitoid or kleptoparasitic wasps, often highly sculptured, with brilliant metallic color ...
''Chrysura refulgens
''Chrysura refulgens'' is a species of cuckoo wasps (insects in the family Chrysididae).
Description
''Chrysura refulgens'' can reach a length of . It is one of the largest South European ''Chrysura''. Head and chest are metallic bluish, while t ...
'' has been recorded as a parasite in the nests of ''O. bicolor'' in Italy.
''Osmia bicolor'' is polylectic
The term polylecty or generalist is used in pollination ecology to refer to bees that collect pollen from a range of unrelated plants. Apis (genus) , Honey bees exemplify this behavior, collecting nectar from a wide array of flowers. Other pre ...
and uses a wide variety of wildflowers to feed on and to collect pollen and nectar from. In Britain it has been recorded as feeding on wood anemone (''Anemonoides nemorosa
''Anemonoides nemorosa'' (syn. ''Anemone nemorosa''), the wood anemone, is an early-spring flowering plant in the buttercup family Ranunculaceae, native to Europe. Other common names include windflower, European thimbleweed, and smell fox, an all ...
''), common bluebell (''Hyacinthoides non-scripta
''Hyacinthoides non-scripta'' (formerly ''Endymion non-scriptus'' or ''Scilla non-scripta'') is a bulbous perennial plant found in Atlantic areas from the north-western part of the Iberian Peninsula to the British Isles, and also frequently used ...
''), heath dog-violet ('' Viola canina''), bird's-foot-trefoil (''Lotus corniculatus
''Lotus corniculatus'' is a flowering plant in the pea family Fabaceae. Common names include common bird's-foot trefoil, eggs and bacon, birdsfoot deervetch, and just bird's-foot trefoil (a name also often applied to other ''Lotus'' spp.). It ha ...
''), horseshoe vetch (''Hippocrepis comosa
''Hippocrepis comosa'', the horseshoe vetch, is a species of perennial flowering plant belonging to the genus '' Hippocrepis'' in the family Fabaceae.
Description
The overall appearance depends on its habitat: sometimes it forms upright clump ...
''), sainfoin (''Onobrychis viciifolia
''Onobrychis viciifolia'', also known as ''O. sativa'' or common sainfoin () was an important forage legume in temperate regions until the 1950s. During the Green Revolution it was replaced by high yielding alfalfa and clover species. Due to its ...
''), willow (''Salix
Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions.
Most species are known ...
'' spp.), ground-ivy (''Glechoma hederacea
''Glechoma hederacea'' is an aromatic, perennial, evergreen creeper of the mint family Lamiaceae. It is commonly known as ground-ivy, gill-over-the-ground,Connecticut Invasive Plant List', Connecticut Agricultural Experiment Station, January ...
''), daisy (''Bellis perennis
''Bellis perennis'' (), the daisy, is a European species of the family Asteraceae, often considered the archetypal species of the name ''daisy''. To distinguish this species from other plants known as daisies, it is sometimes qualified or known a ...
'') and dandelion (''Taraxacum
''Taraxacum'' () is a genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus has a near-cosmopolitan distribu ...
'' sp.).[
]
Conservation
''Osmia bicolor'' is classified as a nationally notable species in Britain,[ although it is classified a Least Concern by the ]International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
and European Commission
The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...
.
References
External links
BBC Radio 4 The Living World Programme on ''Osmia bicolor''
{{Taxonbar, from=Q2938169
bicolor
Hymenoptera of Europe
Insects described in 1781
Taxa named by Franz von Paula Schrank