A number of ants are known that construct extensive underground
dwellings, in which they store seeds of various kinds. Some of the
American species (_Pogonomyrmex_) may be even said to winnow their
grain, for they carefully strip off the husks and deposit these on
rubbish-heaps outside the nest.
Some of the seed-storing ants almost deserve the name of maltsters on
account of the way they deal with their harvest. The human method of
making malt is to allow the barley grains to germinate to a certain
extent until the contained starch is converted into malt-sugar, when the
process is arrested by scalding. In similar fashion ants permit
germination to go on to a certain point, and then kill the seedlings by
biting away the little shoots and roots. In this way a supply of the
sweet food they love is secured.
Among the most interesting of ants are leaf-cutting forms (_Atta_)
native to tropical America. They are associated in huge communities
occupying complex underground dwellings, the sides of which are marked
by mounds that may measure as much as forty yards round. The chief food
consists of a kind of fungus (_Rozites gongylophora_), cultivated on
bits of leaf, and treated in such a way that little white elevations are
produced. It is these that the ants desire.
The chief duty of one set of workers is to collect the pieces of leaf
required. To facilitate their operations, roads, largely underground,
are constructed, which lead to suitable trees, and may be as much as
twenty yards long, or more. Curved pieces of leaf are bitten out and
carried back to the nest, where they are handed over to another set of
workers, by them to be reduced to smaller fragments and made into
mushroom beds.