We remained with them until seven o’clock, when we placed a long bottle over each stem in such a way that while it did not interfere with the work of the wasp, it caught the chips of pith as they fell out. At the end of an hour we noted the amount of accumulation in the tube, and thus had a measure of their rate of work. The drawing gives an idea of the arrangement of the tube on the stem. When we left them they were still digging and delving. At half past nine we took a lantern and went down to visit our charges. We expected to find them at rest, and asleep; but on the contrary they were working as busily as ever, and upon examining the measuring glasses we found that they had not paused since we left them. We measured the depth of the débris in the bottles, and then emptied them. At four o’clock on the next morning we went to the garden, and were much surprised to find that the two wasps had worked without intermission throughout the night. Indeed they seemed to have shortened a little the time that it took to make a round trip down the gallery and up to the opening again, since there was more pith in the bottles than we could have expected if they had worked at only their former rate. Neither the coolness of the air nor the darkness of the night had made the slightest difference to them. After watching them a few minutes, and marveling at their powers of endurance, we cleared out the tubes and returned to bed. At half past eight we found them still at work. Unlike us, they had taken no morning nap, but had gone on with their tunneling in their usual steady way. From this time their ways diverged, and they must be described separately. At nine o’clock the one that we had first seen came up to the opening, walking head first, and flew off, remaining away seven minutes. When she returned she at once resumed her work, and kept at it without a pause until two in the afternoon. At this hour she went away, and we never saw her again. We suppose that she was killed, for it seems improbable that so faithful a creature could have deserted her half–finished home. Pompilus quinquenotatus often deserted a partly finished nest for some more enticing spot, and Sphex started several excavations before making a final choice; but we cannot believe that there was anything fickle about Crabro. The second wasp came up head first to the entrance of her hole at two minutes after nine, as though she had been influenced, in some subtle way, by her neighbor’s example; but after looking about for a moment she went back. She repeated this observation several times, and finally, at twenty–five minutes after nine, came out and flew to a leaf near by. Then she circled around, alighting a number of times, and at last departed. Her stay was brief, for at just thirty–five minutes after nine she returned, and at once settled down to her work.