a heterozygous black (bb) mouse is crossed with homozygous black mouse (bb)
striped_field_mouse is mammal. black_rat is mammal. knockout_mouse is mouse. wood_mouse is mouse. rook is black_bird. ant_lion is neuropteron. cotton_mouse is wood_mouse. black_rook is black_chess_piece. pygmy_mouse is wood_mouse. black_rook is rook.