30 WASP STUDIES AFIELD 



reached the limit of her distance from the hole, she does 

 not wander aimlessly over the area, but always returns to 

 the hole to begin a new series of arcs. This marvellous 

 system of covering the ground is more easily made clear 

 by the accompanying diagram (fig. 5). It is interesting 

 to note that the wasp usually confines its sweeping to the 

 area in front and at the sides of the hole, but is rarely seen 

 working behind the hole. Of course this may be due largely 

 to the fact that the loose dirt all lies in front of the burrow 

 where it has been thrown during the digging. 



Thus she sweeps, spreads and redistributes the loose sur- 

 face dust for a foot or more, until, if we have not the exact 

 location of the nest marked, we can seldom find it, so well 

 is it concealed. Then she circles to and fro on the wing 

 an inch or so above the area, surveying it carefully for sev- 

 eral seconds, and goes whirling off flirtatiously with the 

 other wasps, which, from time to time, have been dabbing 

 down beside her and bumping her. One B. nubilipennis 

 accomplished the permanent closing of her nest in twenty 

 minutes, but they usually require a longer time to finish this 

 critical piece of work. 



When we see such highly developed instinct for the care 

 and safeguarding of the young, we are surprised to find 

 that these mothers are often guilty of committing gross 

 errors in the most fundamental points. We watched one 

 wasp working with great care and precision in closing 

 her nest. After the last superficial trace of the hole had 

 been carefully obliterated and the surrounding ground swept 

 clean and she had departed, we opened the burrow in the 

 full expectation of obtaining a mature larva, but we were 

 shocked to find that the larva had pupated long ago and 

 had been dead and rotten for some days at least. No fresh 

 or uneaten flies were in the chamber; only the old debris. 

 What she could have been doing there, or why she was so 



