INSTINCT AND INTELLIGENCE 



stone or a plant three or four inches to one side, it called 

 upon her to climb, and climb she did, although she was 

 obliged to leave her proper path to do it. 



It is obviously more difficult to distinguish actions of 

 intelligence than of instinct. One must be familiar with 

 the normal conditions of the insects in question before 

 he is able to note those slight changes in the environ- 

 ment that offer some opportunity for an adaptation of 

 means to ends, or before he is competent to devise ex- 

 periments which will test their powers in this direction. 



We find two classes of intelligent actions among the 

 Hymenoptera which are sufficiently distinct to be con- 

 sidered separately, although, like all natural groups, 

 they grade into each other. The first of these includes 

 those actions that are performed by large numbers in a 

 similar fashion under like conditions, while in the sec- 

 ond class each act is an individual affair, as where a 

 single wasp, uninfluenced in any way by the example 

 of those about it, displays unusual intelligence in grap- 

 pling with the affairs of life. Examples of the first class 

 are found in such modifications of instinct as are shown 

 by Pelopaeus and other wasps in the character of their 

 habitations. Pelopaeus, instead of building in hollow 

 trees or under shelving rocks, as was the ancient custom 

 of the race, now nests in chimneys, or under the eaves 

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