Imperium naturæ C. Linnaeus, 1758 - nature
   Mundus Plinius - physical world
     naturalia - natural bodies
       Regnum Animale C. Linnaeus, 1758 - animal kingdom see Kingdom Animalia Linnaeus, 1758
         Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
           Order Picae Linnaeus, 1758 see Parvclass Picae (C. Linnaeus, 1758)
             Genus Merops Linnaeus, 1758
               1 Merops apiaster Linnaeus, 1758 - European bee-eater
               2 Merops viridis Linnaeus, 1758 - blue-throated bee-eater
               3 Merops cinereus Linnaeus, 1758
               4 Merops cafer Linnaeus, 1758 see Promerops cafer (C. Linnaeus, 1758)