SENSE OF DIRECTION 



delayed in this way for forty minutes, when she would 

 have seized the spider and gone on her way without a 

 pause had we not interfered. 



Very often the wind would shake the plant so that 

 the spider or caterpillar would fall to the ground. Under 

 these circumstances the wasp was not at all disconcerted, 

 but, on not finding her prey where she had left it, dropped 

 at once to where it was lying. This is probably only an 

 extension of their ordinary habits. A wasp that takes 

 spiders learns to follow them as they drop from the web 

 on being disturbed. In this they are evidently guided 

 by sight, but perhaps they are also aided by the sense 

 of smell under other conditions, to the extent, at least, 

 of recognizing the place upon which their prey has lain. 

 With so much to build upon, it is easy to see how natural 

 selection may have perfected the habit. We are delaying 

 a long time over details, but we feel that to invoke an 

 unknown sense is permissible only after a careful study 

 of the daily life of the animals in question has left the 

 problem unsolved. 



Among the wasps that first make the nest and then 

 provision the larder, Astata bicolor is one of the most 

 interesting. She makes a permanent abiding-place, 

 and probably uses it until all of her eggs are laid. It 

 is evident that since she comes and goes many times 

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