INTELLIGENCE IN INSECTS 209 
receives from other members of its community numerous 
olfactory, tactile, and perhaps auditory stimulations to 
which it instinctively responds. These stimulations pro- 
duce a condition of general nervous irritability which 
spurs the insects on to activity and makes them ready to 
combine in an attack upon an enemy. Whether or not 
similar effects, as Wagner contends, are produced in solitary 
insects—and I am not convinced that they are, from the 
evidence adduced—it is undoubtedly true that social 
insects are dependent upon the stimuli received from the 
coéperation of others to a remarkable degree. The confusion 
produced by the loss of a queen and the gradual languishing 
of a swarm in which no queen can be supplied, show how 
sensitive are bees to changes in their social environment. 
Among bees, ants and termites signs of anger by one in- 
dividual may awaken the whole community to a high pitch 
of excitement. Each individual then serves to arouse the 
others, and the larger the community the greater the mass 
effect. 
Closely associated in many cases with the influence of 
numbers is the effect of imitation. The activities of insects 
not only arouse the energies of their fellows, but they also 
direct their efforts and in this manner secure coéperation 
toward a common end. Ants keep together in their forag- 
ing expeditions and often follow the “scouts” which act 
as leaders, guiding the expedition to the nest to be pillaged. 
“Tn artificial nests,’ says Wheeler, “one usually sees a 
particular activity started by one or a few workers, which 
have more initiative or respond more quickly to a change 
of conditions than the great bulk of the colony. The move- 
ments of such individuals attract the attention of others in 
their immediate neighborhood and these forthwith proceed to 
imitate their more alert companions. Then the activity 
14 
