ait for prey;
and they escape from their enemies mainly through strength, speed,
concealment, or other physical powers or methods. Escape may
occasionally develop mental alertness, but does not usually do so.
Certainly if the alert, watchful, suspicious habits of the apes are due
to the requisite of avoiding dangerous enemies, we might naturally look
for similar habits in the lemurs, which are similarly situated. And if
we consider the wide distribution of the apes throughout the tropics of
both hemispheres, and their great diversity in species and condition, it
seems very unlikely that in all these localities their relations with
other animals would be such as to develop the mental alertness which
they so generally display. The fact appears to be that, while this may
be a cause, it is not a leading cause, of mental development in animals,
and that we must seek elsewhere for the origin of animal intelligence.

Research, indeed, leads us to examples of intelligence where we should
least expect to find it. Among the mammalia we perceive one marked
example in the beavers, the only one in the great class of the rodents,
with their nine hundred or more of species. But we must go still lower,
to the insects, for the most striking examples, finding them alone in
the ants, the bees, and the termites, among the vast multitude of insect
forms. Less marked instances appear in the elephants, in some of the
birds, and in certain other gregarious animals.

From these examples, and what is elsewhere known of animal intelligence,
one broad conclusion may be drawn, that all the strikingly intelligent
animals are strongly social in their habits, and that no decided display
of intelligence is to be found among solitary species. This conclusion
becomes almost a demonstration in the case of the ants and bees. The
ants, for instance, comprise hundreds of species, spread over most of
the world, mainly social, but occasionally solitary. The social species,
while varying greatly in habit, all display powers of intelligence, and
these so diversified as to indicate many separate lines of evolution.
The solitary ants, on the contrary, manifest no special intelligence,
and do not rise above the general insect level. The same may be said of
the bees. The hive bee, the most communal in habit, shows the highest
traits of intelligent activity. The bees which form smaller groups and
the social wasps stand at a lower level, and the solitary bees and wasp