216 THE SOLITARY WASPS. 



portant it was not to disarrange the grass or plants on such oc- 

 casions. The wasps are in many cases so prudent as to conceal 

 their booty among the leaves and this made 5t very inconvenient 

 to keep our eyes upon the captured prey, as was quite necessary 

 if we wished to follow it on its travels. To avoid the discom- 

 fort of lying on the ground or of twisting the neck at some im- 

 possible angle for half an hour at a time, we sometimes gently 

 moved the intercepting objects to one side, but even such a 

 slight change cost us dear in time and patience as it threw the 

 wasp out of her bearings and made it difficult for her to recover 

 her treasure. "We recall one exceedingly warm day in Septem- 

 ber when we were 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 circum- 

 stances 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 evi- 

 dently 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 only 

 permissible 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 during the several weeks of her occupation she 

 does not need to make a prolonged study of the environment at 

 every departure. Her first survey, just after the nest is com- 



