A small dark-coloured bee with two submarginal cells in the forewing, and a coarsely punctate body.  The resin bees have a distinctive curved ridge on the dorsal surface of the first abdominal segment.  Female have an orange pollen-brush beneath the abdomen.  Nests are made in exisiting holes in dead wood or walls. 

Some smaller mason bes (Osmia), or larger scissor bees (Chelostoma)

Close examination of a specimen is needed to see the diagnostic ridge on the tergite

Grassland, brownfield land, gardens and open sites, usually with Ragwort or other plants in the Asteraceae.

Summer

It appears to be exanding its range northwards from the south-east