AMMOPHILA AND HER CATERPILLARS 



she found one which fitted into the hole exactly, and 

 after placing it she brought a much smaller piece which 

 she put above and to one side. She then stood back 

 and surveyed the whole, and it seemed to us that we 

 could read pride and satisfaction in her mien. She then 

 flew away, and we supposed that that stage of the work 

 was completed. Upon coming back two hours later, 

 however, we found that she had been trying some more 

 improvements, as a number of little pellets had been 

 piled up over the nest. This wasp, by the way, never 

 succeeded in finding a caterpillar, since when we opened 

 the burrow a few days later it was still empty. Perhaps 

 she came to some untimely end. 



Of the other wasps that we saw making a temporary 

 closure of their nests, one wedged a good-sized stone 

 deep down into the neck of the burrow and then filled 

 the space above, solidly, with smaller stones and earth. 

 Another placed two lumps of earth just below the sur- 

 face of the ground, filled the opening with pellets loosely 

 thrown in, and then kicked some light dust over the 

 whole. The others used only two or three lumps of earth, 

 which they fitted neatly into the opening just below the 

 surface. Although it is usual for urnaria to leave her 

 nest closed while she is off searching for her prey, there 

 is no invariable rule in the matter, even for single individ- 



33 



