her attendant guards to visit the royal cells, whose occupants
she stings to death, thus destroying any possible claimant to her place.
And when the royal princess constructs her part of the pupal case, she
leaves an aperture so that if and when it should become necessary for the
queen to kill her, the sovereign would not injure her sting and be unable
to kill the other individuals who might become aspirants for the throne
and so precipitate a civil war! As in the case of the self-destructive act
on the part of a stinging cell in _Hydra_, altruistic subservience to the
interests of the colony can go no farther.

The ants form stable colonies of still higher grades, where the workers
are not all alike in general structure, but become more rigidly
specialized for the performance of restricted tasks. As before, there is
the fundamental differentiation into the sexual "queens" and males, and
the sterile workers concerned with the immediate material life of the
community. In some species the workers serve as herdsmen, caring for the
ant-cattle or aphids, from which they receive minute drops of a sweet
juice for food. The aphids are tended on the leaves of various plants
during the summer, and are carefully reared and stabled and fed below
ground during the winter months. In other species seeds are procured and
stored in underground granaries. The leaf-cutters are forms which grow
food supplies of fungi in subterranean mushroom gardens; the compost
consists of cuttings brought from the leaves of bushes by myriads of
workers, whose processions are guarded by larger-headed soldiers of
several ranks. In the honey-ants of Colorado and tropical America certain
individuals pass their time suspended from the roof of a large
nest-chamber, where they receive the sweet juice brought in by the workers.
They serve as animated preserve jars, distended sometimes to the size of a
grape with the communal stores of food, which they return to the workers
when external sources of food may fail. Finally there are the slaveholding
species which conduct forays upon the nests of other forms, to procure the
young of the latter, which grow up in their captors' nests and serve them
as nurses and masons and foragers. So long has this custom been
established that some slaveholders are entirely unable to feed themselves,
and would die out if their slaves failed to support them.

* * * * *

Let us pause at this point to su