THE EUMENIDAE 315 



the economy of this elaborate method of work. In a half- 

 hour she had deepened her hole just the length of her own 

 body ; other wasps, such as Priononyx or Sphex, digging and 

 kicking out the dirt, would have progressed much faster. 



With this supply of water, she worked 7 minutes and took 

 out 1 1 loads of earth, after which she surprised us by flying 

 off toward the northeast. A quarter of an hour elapsed 

 before she returned. She must have found a supply of water 

 somewhere in that direction, however, for she resumed work 

 normally, taking out 12 mud-balls in just eight minutes. 

 On the next two journeys, she resumed her northwesterly 

 course; the first time she made the trip in one minute and 

 the next time in only one-half minute. Can it be that she 

 was learning by experience to make her trips more quickly 

 or directly? 



By this time we were sufficiently familiar with her usual 

 course to make it comparatively easy to follow her in 

 her flight to her watering-place, except that it required 

 such sprinting as was neither becoming to our mature fig- 

 ures nor befitting to a July day. The pond, a mere puddle 

 of rain-water which remained in a small depression, was 

 some 200 feet distant. When she arrived she went direct to 

 the edge of the clearest part of the puddle, took a long drink, 

 and when she arose in flight she seemed very heavy on the 

 wing, probably because of being gorged with water. We 

 were surprised to find that even after she had made so 

 many trips to the pond, her course was not quite direct. In- 

 stead, her going out and her return to the nest followed the 

 course indicated in the little diagram, the left in figure 59. 

 She flew west-by-northwest to the railroad track, down the 

 track to a point even with her tiny pond, then to the pond 

 and home again, with only a minor detour in her return 

 route, as indicated. 



This time she worked only 5 minutes and removed 7 



