Bombus vestalis is a cuckoo bumble bee in the subgenus Psithyrus. Cuckoo bumble bees are considered “social parasites” because they exploit an entire host colony of a different bumble bee species, tricking the host workers into rearing the cuckoo’s brood. (Photo credit: Steven Falk, originally published in Lhomme and Hines 2018, Annals of the Entomological Society of America)