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INTELLIGENCE IN INSECTS 201 
concludes, “can only be explained by an association of space 
form and color memories with memories of taste.” 
We are certainly justified in concluding that insects are 
not mere reflex machines incapable of learning by experience. 
They can form associations very quickly in many cases. 
They give evidence of memory.” They have a remarkable 
ability for retaining impressions of topographical relations. 
We may not be compelled to admit that they have ideas, 
but it must be granted, I think, that a wasp which after 
cutting a caterpillar in two and carrying away one part, 
came back and searched diligently for the remainder, re- 
tained somehow an impression of the missing part and its 
location. If out of sight it was not out of mind. The hunt- 
ing of the wasp is instinctive and when we see a wasp 
flitting about here and there in a feverish search for prey 
we cannot assume that it carries in its mind an image of the 
object of its pursuit. But the case is different with a wasp 
which has secured its prey and comes back to find it. The 
prey and its position are represented by some sort of “en- 
gram” in the nervous center of the wasp, which is formed 
by the various stimuli, optical, olfactory and tactual, which 
resulted from the encounter. If the wasp does not have an 
idea of its prey it has something which plays a réle similar 
to that of ideas in ourselves. As the wasp when it has 
disposed of the second moiety of the caterpillar no longer 
returns, its mental content is evidently changed by having 
carried the part to its nest. If there is something represent- 
ing “part-of-caterpillar-among-leaves” that leads the wasp 
on its hunt, we may conclude that there is also something 
corresponding to “ part-of-caterpillar-now-in-nest” which 
prevents further search. 
I realize that one is on treacherous ground in trying to 
interpret the workings of the insect mind. Forel, whose 
