LEMMINGS IMPORTANT First of the factors involved is, of course, the vegetation; the grasses, herbs, and tiny dwarf shrubs of the Arctic barrens. The next are the lemmings, mouselike creatures of the Far North that eat the vegetation. They are the first step in turning grass into flesh and fur and feathers. One of the striking facts of lemming biology is the fluctuation in their numbers. Some years they swarm, lemmings are everywhere, and in places they erupt in vast emigration, the tundra and the sea ice being covered with masses of moving lemmings. We know this best from the accounts written about the lemmings of Norway, but the same thing occurs in the American Arctic. At other times they're scarce and it is difficult to find even one. Strangely there's a periodicity in this, and periods of abundance and scarcity tend to recur every four years. What happens or what causes it we don't know. The Arctic fox, staple fur bearer of the Far North, and the snowy owl both prey on lemmings. Lemmings are so important to them that when lemmings are abundant the foxes and the owls prosper and multiply; when the lemmings are scarce the foxes and the owls starve or migrate, in any case where there are few lemmings there are few foxes or owls. Thus we see how it is that an abundance of snowy owls can indicate that the Eskimo will make a good fox catch and the trader will do good business. MONKEY BIRDS [Illustration] Birds get their everyday names in a variety of ways in the countries where they live; from their looks, like the snake birds and the pond scroggins; from their color, like the cardinal and the blackbird; from their behavior, like the frigate bird and the creepers and the boobies and king-birds; from what they eat, or are supposed to eat, like the antbirds and plantain eaters and bee eaters; from what they say, like the poor-will and the more-pork; from how they say it, like the warblers and the screamers; from how often they say it, like the brain-fever bird and the wideawake terns; from where they nest, like the cliff swallow and the house martin and the chimney swift; and some from their non-bird associates, like the cowbird, moose-bird, and the monkey bird. It is the monkey birds that have taken our fancy at the moment. The forests of Africa, the jungles of Borneo, and the forests of the Philippine Islands each have a bird that associates so often with monkeys that this habit became incorporated into its local name. The birds are not at all closely related. One is a hornbill, one is a drongo shrike, and one is the fairy bluebird. The hornbill goes in parties of their own kind, but apparently the drongo, and certainly the fairy bluebird prefer the society of monkeys to that of their own kind.