w till it can be imbibed by the ants. This circlet is lacking in
aphids that are rarely or never visited by ants.

4. Certain observations go to show that aphids, when visited by ants,
extract more of the plant juices than when unattended.

The adaptations on the part of the ants are, with a single doubtful
exception, all modifications in behavior and not in structure.

1. Ants do not seize and kill aphids as they do when they encounter
other sedentary defenseless insects.

2. The ants stroke the aphids in a particular manner in order to make
them excrete the honey-dew, and know exactly where to expect the
evacuated liquid.

3. The ants protect the aphids. Several observers have seen the ants
driving away predatory insects.

4. Many aphidicolous ants, when disturbed, at once seize and carry their
charges in their mandibles to a place of safety, showing very plainly
their sense of ownership and interest in these helpless creatures.

5. This is also exhibited by all ants that harbor root-aphids and
root-coccids in their nests. Not only are these insects kept in
confinement by the ants, but they are placed by them on the roots. In
order to do this the ants remove the earth from the surfaces of the
roots and construct galleries and chambers around them so that the
Homoptera may have easy access to their food and even move about at
will.

6. Many ants construct, often at some distance from their nests, little
closed pavilions or sheds of earth, carton, or silk, as a protection for
their cattle and for themselves. The singular habit may be merely a more
recent development from the older and more general habit of excavating
tunnels and chambers about roots and subterranean stems.

7. The solicitude of the ants not only envelops the adult aphids and
coccids, but extends also to their eggs and young. Numerous observers
have observed ants in the autumn collecting and storing aphid eggs in
the chambers of their nests, caring for them through the winter and in
the spring placing the recently hatched plant lice on the stems and
roots of the plants.

In the foregoing I have discussed the ethological relations of ants to a
variety of other organisms. This, however, did not include an account of
some of the most interesting symbiotic relations, namely, those of the
ants to other species of their own taxonomic group and to termites. This
living together of colonies of different species may be properly
designated as social sy