cuckoo bee

from The Collaborative International Dictionary of English v.0.48

cuckoo bee \cuckoo bee\ n. (Zool.),
   a bee, parasitic in the larval stage in the nests of other
   bees, feeding either upon their food or larvae. They belong
   to the genera {Nomada}, {Melecta}, {Epeolus}, and others.
   [1913 Webster]