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 Passeres Linnaeus, 1758 see Suborder Passeres (C. Linnaeus, 1758) C. Linnaeus, 1766
             Genus Hirundo Linnaeus, 1758
               1 Hirundo rustica Linnaeus, 1758 - barn swallow
               2 Hirundo esculenta Linnaeus, 1758 see Collocalia esculenta (C. Linnaeus, 1758)
               3 Hirundo urbica Linnaeus, 1758 see Delichon urbicum (C. Linnaeus, 1758)
               4 Hirundo riparia Linnaeus, 1758 see Riparia riparia (C. Linnaeus, 1758)
               5 Hirundo apus Linnaeus, 1758 see Apus apus (C. Linnaeus, 1758)
               6 Hirundo subis Linnaeus, 1758 see Progne subis (C. Linnaeus, 1758)
               7 Hirundo pelagica Linnaeus, 1758 see Chaetura pelagica (C. Linnaeus, 1758)
               8 Hirundo melba Linnaeus, 1758 see Tachymarptis melba (C. Linnaeus, 1758)