This is an attractive mining bee which is very scarce and poorly known in Ireland, having been recorded on just four occasions. It is similar to Andrena scotica, but both sexes have subtle red markings on the margins of the first and second tergites, as well as on sternites 1 and 2 (see images below). The red colouration is more pronounced in the summer generation. Compared to female A. scotica, A. trimmerana typically has a harier abdomen with a slightly more ‘banded’ look, due to the lightened hind margins of the tergites. The males possess a narrow spine adjacent to the base of the mandibles, which A. scotica lacks. They also have a pale marking on the hind tibia, which males of the similar Andrena rosae lack. The extreme paucity of records mean it is classed as Critically Endangered.

Distribution in Ireland: The four records all come from Cos. Dublin and Carlow, suggesting a very localised southeastern distribution pattern here.

Flight period: A bivoltine specues, flying from mid-March until mid-May and again from early July until late August, although this infomation is based on British data and it has only ever been found in Ireland during April and May.

Habitat: Precise associations are unknown, but specimens have been recorded in a deciduous woodland clearing, along a scrubby lowland field margin and in mature parkland. It probably prefers woodland edges and scrub here with abundant spring-flowering shrubs and summer-flowering brambles and umbellifers

Flowers visited: No Irish data exists. Spring individuals likely visit Blackthorn, Hawthorn, Alexanders and willows as they do in Britain. Summer specimens probably rely on brambles and Hogweed.

Personal records: I have only observed this species on one occasion, which was a solitary female basking in grassy vegetation in a deciduous woodland clearing.