GENERAL CONSIDERATIONS 363 



with eagerness, expressing in every movement and attitude 

 the furious eagerness and excitement which agitated her. 



Finally, we arrive at the items of behavior evidencing 

 intelligence, or let it be called plastic judgment, practical 

 judgment, place-memory, associative memory or aptitude 

 for learning. Only a few instances, to be sure, may be 

 recalled here. 



Late in the mating season of Bembix nubilipennis, the 

 males mate with the females quietly, right on the dancing 

 area, whereas only a few days earlier, when males are abun- 

 dant and females few, the marriage flight consists of a wild 

 dash far out over the grass outside the dance area and away 

 from the mobs that were ready to sever the mating pair. 



One Bembix started one hole after another, while fre- 

 quently others would fly down and alight with a thump and 

 violently bump her. Each time she was bumped she flew a 

 short distance and began a new hole. After eight such at- 

 tempts, she learned not to mind intruders further and con- 

 tinued to dig the last hole while twenty-four other wasps 

 one by one flew down and butted her. 



While the temporary closing of the burrow of Bembix 

 by kicking up loose soil is probably instinctive, we believe 

 the insect uses plastic judgment in meeting some conditions. 

 When the ground is packed hard by dashing rains, she labor- 

 iously bites out with her mandibles the fililng, and after per- 

 manently closing her burrow, she sweeps the dirt so as to 

 remove from the surface all traces of her nest. Her conduct 

 here varies with conditions; if there is a surplus of loose 

 dirt near the hole, she sweeps it away and scatters it evenly 

 over a considerable area; if it is bald so that traces of the 

 filled hole are evident, she sweeps other dust back over it 

 for .a distance until no trace of a scar can be seen. 



The behavior of Sphex pictipennis in overcoming un- 

 usual difficulties in getting her caterpillar through a tangle 



