ompany attacks the inner bark, which is the
favorite morsel, leaving the coarse outer bark untouched, or more
usually replacing it with grains of earth, atom by atom, as they eat
it away. The inner bark is gnawed off likewise as they go along, but
the woody tissue beneath is allowed to remain, to form a protective
sheath for the second company, who begin work at the centre. This
second contingent eats its way outward and onward, leaving a thin
tube of the outer wood to the last, as props to the mine, till they
have finished the main excavation. When a fallen trunk lying upon the
ground is the object of attack, the outer cylinder is frequently left
quite intact, and it is only when one tries to drag it off to his
camp-fire that he finds to his disgust that he is dealing with a mere
hollow tube, a few lines in thickness, filled up with mud.

But the works above ground represent only a part of the labors of
these slow-moving but most industrious of creatures. The arboreal
tubes are only the prolongation of a much more elaborate system of
subterranean tunnels, which extend over large areas and mine the earth
sometimes to a depth of many feet or even yards.

The material excavated from these underground galleries and from the
succession of domed chambers--used as nurseries or granaries--to which
they lead, has to be thrown out upon the surface. And it is from these
materials that the huge ant-hills are reared, which form so
distinctive a feature of the African landscape. These heaps and mounds
are so conspicuous that they may be seen for miles, and so numerous
are they and so useful as cover to the sportsman, that without them in
certain districts hunting would be impossible. The first things,
indeed, to strike the traveler in entering the interior are the mounds
of the white ant, now dotting the plain in groups like a small
cemetery, now rising into mounds, singly or in clusters, each thirty
or forty feet in diameter and ten or fifteen in height; or again,
standing out against the sky like obelisks, their bare sides carved
and fluted into all sorts of fantastic shapes. In India these
ant-heaps seldom attain a height of more than a couple of feet, but in
Central Africa they form veritable hills, and contain many tons of
earth. The brick houses of the Scotch mission-station on Lake Nyassa
have all been built out of a single ants' nest, and the quarry from
which the material has been derived forms a pit beside the settlement