Bombus bellardii is a species of cuckoo bumblebee. It is known commonly as the indiscriminate cuckoo bumblebee. This species is a host to "Bombus insularis", a species of cuckoo bumblebee. Bombus variabilis is a critically endangered species of cuckoo bumblebee. This species is host to the parasitic cuckoo bumblebee "Bombus insularis". It may be a host to Fernald's cuckoo bumblebee ("B. fernaldae"). The nest is sometimes parasitized by the cuckoo bumblebee "Bombus citrinus". Bombus campestris is a very common cuckoo bumblebee found in most of Europe. Bombus rupestris is a species of cuckoo bumblebee present in most of Europe except Iceland.