In Minnesota, 23% of bee species are cuckoo bees. Cuckoo bees, also called cleptoparasitc bees or brood parasites, do not build their own nest. Instead, they lay their eggs in the nest of another bee (host), and their larvae consume the pollen provisions provided by the host. The host egg or larva must be destroyed after an egg is laid by the cuckoo bee. Many cuckoo bees leave this task to their larvae. In one of their instar stages, usually the non-feeding first instar stage, the larvae develop large mandibles that they employ to destroy the host egg or larvae. There are also social parasites: Cuckoo bumble bee (Bombus) females take over an active social Bombus nest and eliminate the host queen. In addition, sweat bees in the genus Lasioglossum invade and occupy social nests of bees in the same genus. In Minnesota, there are 11 genera and 120 cuckoo bee species that occur within three (of six) families.  

Cuckoo bees that are brood parasites of solitary bees are wasp-like in appearance, have pitted exoskeletons and other anatomical features that help protect them if they are attacked by the host bee. They lack pollen-collecting structures and other nest-building anatomy such as soil moving and tamping structures present in ground-nesting bees or anatomical features that cavity-nesting bees use to collect supplemental nesting materials. One theory proposed to explain why some cuckoo bee females evade detection by their host is that they have a similar "smell" or chemical signature as the host.