 Many species of Bombus , including the group sometimes called Psithyrus ( cuckoo bumblebees ) , have evolved Müllerian mimicry , where the different bumblebees in a region resemble each other , so that a young predator need only learn to avoid any of them once . For example , in California a group of bumblebees consists of largely black species including B. californicus , B. caliginosus , B. vandykei , B. vosnesenskii , B. insularis and B. fernaldae . Other bees in California include a group of species all banded black and yellow . In each case , Müllerian mimicry provides the bees in the group with a selective advantage . In addition , parasitic ( cuckoo ) bumblebees resemble their hosts more closely than would be expected by chance , at least in areas like Europe where parasite @-@ host co @-@ speciation is common ; but this too may be explained as Müllerian mimicry , rather than requiring the parasite 's coloration to deceive the host ( aggressive mimicry ) . 
