This is the most widely-recorded of the species in the subgenus Psithyrus in Ireland, commonly known as the cuckoo bumblebees.  It is however not particularly common and is listed as Near Threatened. Females resemble several other cuckoo species but the combination of lemon-yellow hairs fringing the white tail and a rather ‘fluffy’, less striking appearance when compared with Bombus vestalis are useful characteristics. Males can also be tricky to reliably identify, but the yellow hairs fringing the white tail is a useful feature and compared to its most similar relative B. vestalis, it is usually a bit fluffier with more prominent and slightly lighter yellow banding on the thorax and abdomen. More reliably, the antenna segments 3 and 5 are uniform in length compared to uneven lengths in B. vestalis. Generally speaking it is much commoner in Ireland than B. vestalis, which is very rare. Its host species are members of the Bombus lucorum group, which includes B. magnus and B. cryptarum.

Distribution in Ireland: Widespread throughout, but never common.

Flight Period: Females emerge in late March and males in May. It can be seen into October.

Habitat: Various, including scrub, woodland clearings, bogland, coastal grassland and gardens.

Flowers visited: Dandelion, knapweeds, thistles, Devil’s-bit Scabious, brambles and others.

Personal Records: This is a species I have encountered infrequently. I found single males in a bog outside Roscommon town and in unimproved grassland near Tullamore (Co. Offaly). I have also encountered males and females feeding on Common Knapweed in a calcareous grassland nearby in Co. Roscommon. I have observed females in a bog near Brookeborough (Co. Fermanagh) and in the Glendalough area (Co. Wicklow). The host species are members of the Bombus lucorum species complex, with the distributional data suggesting that B. magnus or B. cryptarum may be preferred.