INTELLIGENCE IN INSECTS 205 
“mere instinct” will not account. In most cases there 
has been no previous study of the animal’s behavior with a 
view to ascertaining the nature and limitations of its instinc- 
tive performances. Ants are observed to build bridges over 
water or other substances which they are desirous of crossing, 
by bringing grains of sand or bits of earth and dropping them 
until they can effect a passage. The ants are then credited 
with ingenuity, reason, imagination and other mental 
qualities which human beings would employ to overcome a 
similar difficulty. And taken by themselves the facts 
seem to justify such conclusions. Light on the matter, 
however, is thrown, as in so many other cases, by a study of 
the creature’s instincts, which shows that the apparent feat 
of engineering is the result of an instinctive propensity of the 
ant, slightly modified perhaps to meet the particular occasion. 
Wasmann, in an instructive experiment, placed on the 
nest of Formica sanguinea a watch glass filled with water 
in the center of which was a sort of island on which were 
isolated a few pupe. The ants brought sand and threw 
it into the watch glass until they had formed a passage way 
to the pup, which were then carried away. Ingenuity, 
surely, one is tempted to say! But the next experiment 
inspires caution. A watch glass with no island and no pupe 
was placed in the nest. This was filled like the previous one. 
At least one important factor in the ants’ activities is the 
instinct to cover offending objects which cannot be removed 
—an instinct analagous to that of bees, which leads them to 
cover over with propolis objects too large to remove from the 
hive. If a dog performed similar actions in endeavoring to 
reach an object otherwise inaccessible we should be justified 
in attributing to the animal a considerable degree of intelli- 
gence. Some intelligence may have been involved in the 
behavior of the ants, but not necessarily more than a very 
