260 THE HISTORY OF CREATION, 
no wild oxen and horses, as in the neighbouring parts of 
South America, both north and south of Paraguay. This 
surprising circumstance is explained simply by the fact that 
in that country a kind of small fly is very frequent, and is 
in the habit of laying its eggs in the navel of newly-born 
calves and foals. The newly-born animals die in conse- 
quence of this attack, and the small deadly fly is therefore 
the cause of oxen and horses never becoming wild in that 
district. Supposing that this fly were destroyed by some 
insect-eating bird, then these large mammals would grow 
wild in Paraguay, as well as in the neighbouring parts of 
South America ; and as they would eat a quantity of certain 
species of plants, the whole flora, and, consequently again, 
the whole fauna of the country would become changed. It 
is hardly necessary to state, that at the same time the whole ~ 
economy, and consequently the character, of the human 
population would alter. 
Thus the prosperity, nay, even the existence of ahole 
populations can be indirectly determined by a single small 
animal or vegetable form in itself extremely insignificant. 
There are small coral islands whose human inhabitants live 
almost entirely upon the fruit of a species of palm. The 
fructification of this palm is principally effected by insects, 
which carry the pollen from the male to the female palm 
trees. The existence of these useful insects is endangered 
by insect-eating birds, which in their turn are pursued by 
birds of prey. The birds of prey, however, often succumb 
to the attack of a small parasitical mite, which develops itself 
in millions in their feathers. This small, dangerous parasite, 
again, may be killed by parasitical moulds. Moulds, birds 
of prey, and insects would in this case favour the prosperity 
