Зависимые списки с подгрузкой данных из JSON

function ajax() { 
  var json = { 
    "ants": [{ 
        "rod": "Messor", 
        "vid": [{ 
            "vname": "Structor" 
          }, 
          { 
            "vname": "Minor" 
          } 
        ] 
      }, 
      { 
        "rod": "Camponotus", 
        "vid": [{ 
            "vname": "Vagus" 
          }, 
          { 
            "vname": "nicobarensis" 
          } 
        ] 
      }, 
      { 
        "rod": "Lasius", 
        "vid": [{ 
            "vname": "Niger" 
          }, 
          { 
            "vname": "Flavus" 
          } 
        ] 
      } 
    ] 
  }; 
  return new Promise(function(res) { 
    return res(json); 
  }); 
} 
var $select = $('#people'); 
var $selectVid = $('#vid'); 
ajax().then(function(data) { 
  $select.html(''); 
  $select.append(data.ants.map(function (val, key) { 
    return '<option value="' + key + '">' + val.rod + '</option>'; 
  })); 
  $select.on('change', function () { 
    var index = $(this).val(); 
    $selectVid.empty() 
      .append(data.ants[index].vid.map(function (val) { 
        return '<option id="' + val.vname + '">' + val.vname + '</option>'; 
    })); 
  }).change(); 
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> 
<select id="people"></select> 
<select id="vid"></select>