THE TOILERS OF THE NIGHT. 47 



all that is restless, vying with the humming-birds in swiftness 

 and energy, while the other is calm, quiet, and stately in all that 

 she does. 



Some ten feet away was a second stirpicola at work, and this 

 one, to judge from the depth to which she had penetrated, must 

 have been at work for about two hours. We watched them 

 both and saw them bring up load after load of pith. They bit 

 out the pellets with their mandibles and passed them back be- 

 tween the legs and under the body until a quantity had accum- 

 ulated above the tip of the abdomen. They then walked back- 

 ward up the stem and thus pushed out the mass as they came to 

 the top. Often they used the hind legs to assist in getting it out 

 of the way, sometimes kicking it to a little distance. Once in 

 every two or three trips they would come out far enough -to ex- 

 pose part of the thorax. They appeared and disappeared with 

 the regularity of a machine, never stoping to rest. 



"We remained with them until seven o'clock when we placed a 

 long large bottle over each stem (PL XI., fig. 7), in such aj 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 

 debris in the bottles and then emptied them for the night. 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 

 wUhout 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 



