Cuckoo bees are less hairy than true bumblebees and usually less active. Females never carry pollen and have no pollen baskets. Males are even more lethargic. There are no workers.
The systematic names of cuckoo bees has changed recently (c. 2003) and older references to cuckoo bees may use the genus name Psithyrus rather than the more modern Bombus as used here.

Bombus bohemicus

Gypsy Cuckoo Bee

Widespread and relatively common. Takes over nests of the White tailed bumblebee (B.lucorum). It has a long shaggy coat, dull yellow collar, and no yellow band on the abdomen. It has a white tail.
  • In the females (Queens) there are two yellow patches before the white tail, forming a faint broken band of yellow but the yellow fades rapidly. There are a few pale yellow hairs at the rear of the abdomen. The species has prominent callosities, which do not meet in the middle.
  • Males are difficult. They are like the female but the white or yellowy tail ends with some black hairs. A microscope to examine the genital capsule may be required.

Bombus barbutellus

Barbut's Cuckoo Bee

Takes over the nests of the Garden Bumblebee (B.hortorum). Local. It has a dingy collar, and a sparse covering of yellow hairs which span the rear of the thorax and the top of the abdomen, which otherwise is mostly black, except that the tail is white.
  • Females have a rounded thorax and abdomen. The last dorsal plate is densely pitted and has a distinct keel.
  • Males have a more pear-shaped abdomen, so that the while tail appears longer. The tip is black.

Bombus sylvestris

Four-coloured Cuckoo Bee

Takes over the nests of the early bumblebee (B.pratorum) and Heath bumblebee (B.jonellus). Uncommon. Quite similar to the previous species, and it is the male that is the easiest to identify by the fringe of red hairs at the end of the rather square tail. When the bee is active, it also curves under the abdomen more strongly than any other bee.
  • The female has a yellow collar on the otherwise black thorax, and sometimes a faint indication of a yellow line at the rear. The second segment of abdomen is wholly black, the next two are white with a tinge of yellow, the fifth segment is black, but the tip is white.
  • The male is similar but has more yellow or white on the tail, ending with a fringe of red hairs at the very tip.

Bombus campestris

Field Cuckoo Bee

Takes over nests of the Common carder bee (B.pascuorum). Uncommon. This bee has two colour forms - a light and a dark. The coat is very thin and much of the abdomen is entirely bare, showing the shining plates. It has a broad dark yellow collar and a second dark yellow band at the rear of the black thorax, and the abdomen is entirely black except for a yellow tip. In the dark form, one or both of the yellow bands on the thorax may be absent.
  • In the female, the yellow at the tail has a dark notch in the middle
  • In light males, most of the abdomen is yellow, whereas dark specimens are wholly black, except for a dingy yellow at the tip of the abdomen.