Ceratina cyanea

This species is present in most of Western Europe, in North West Africa and in the eastern Palearctic realm (excluding China). [2][1][3][4]

This undemanding species colonize both dry habitats and wetlands. It inhabits forest edges, thickets and gardens.[5][6]

Digging the nest

Ceratina cyanea can reach a length of 5–9 millimetres (0.20–0.35 in) (females) and 5–7 millimetres (0.20–0.28 in) (males).[5] Head, chest and abdomen show a metallic blue colour.[5][7] These bees have three submarginal cells in forewings,[8] club-shaped antennae[5] and a long thin tongue.[5] The scutellum is densely punctured. The seventh tergite has a deep saddle and ends in two points.[3][9]

The blue carpenter bees fly from mid-March to mid-October,[5] collecting pollen at various families of plants, especially knapweed (Centaurea), yellow composites (Asteraceae) and Lotus (Fabaceae).[6]

Females dig the nest extracting the soft tissue that fills the cavities of the vertical or slanted dry plant stems and small branches,[7][6] such as thistles, blackberries (Rubus species),[7] elderberries (Sambucus species) and roses.[5][7] Then they provide the cells with a mixture of regurgitated nectar and pollen to feed the larvae.[5] Adult males and females overwinter inside their cells into the stems. Often several insects spend the winter together.[5]