f leaf, about the size of a
sixpence, held vertically between the jaws, is then borne off to the
formicarium. This consists of low wide mounds, in the neighbourhood of
which no vegetation is allowed, probably in order that the ventilation
of the underground galleries may not be interfered with.

For a long time there was considerable doubt as to the use to which
the leaf-cutting ants put the leaves; some naturalists supposed they
are used directly as food, others that the ants roof their underground
dwellings with them. The question was set at rest by Fritz Mueller, who
observed these ants in Brazil,[61] and independently by Belt, who
studied them in Nicaragua, and has written an interesting account of
their proceedings.[62] The real use of the leaves is as manure on
which to grow a minute species of fungus; these ants are, in reality,
mushroom growers and eaters. Belt several times exposed the
underground chambers to observation and found that they were always
about three parts filled with "a speckled, brown, flocculent,
spongy-looking mass of a light and loosely-connected substance."
Scattered throughout these masses were the pupae and larvae, together
with the smallest division of workers who do not engage in
leaf-carrying, but whose duties appear to be to cut up the leaves into
small fragments and to care for the young. On examination the masses
proved to be composed of "minutely sub-divided pieces of leaves,
withered to a brown colour, and overgrown and lightly connected
together by a minute white fungus that ramified in every direction
throughout it." That they do not eat the leaves themselves was shown
by the fact that near the tenanted chambers were found deserted ones
filled with the refuse of leaves that had been exhausted as manure,
and which served as food for the larvae of various beetles. There are
numerous holes leading up from the underground chambers, and these are
opened out or closed up, apparently in order to regulate the
temperature below. Great care is also taken that the nest should be
neither too dry nor too damp; if a sudden shower comes on the leaves
are left near the entrance, and carried down when nearly dry; during
very hot weather, on the other hand, when the leaves would be parched
in a very short time, the ants only work in the cool of the day and
during the night. Occasionally, inexperienced ants carry in grass and
unsuitable leaves; these are invariably brought out again and thrown
awa