A WEEK WITH A MINING EUMENID. 165 



these larva; were obtained by robbing home-coining wasps; the 

 majority were obtained by excavating nests that had been stored 

 and sealed. Fifteen such experiments zvere performed. On one 

 occasion, when I had dropped two caterpillars into a nest, the wasp 

 left the burrow and went hunting without removing them. Later 

 in the day she took two caterpillars from her nest and carried them 

 to the field; but there is no way of telling if these were the two 

 added. On another occasion, when three caterpillars had been 

 dropped into a nest and two deposited on the ground near the 

 nest, the wasp, on emerging, captured one of the caterpillars that 

 had been placed on the ground near the nest, flew with it to a 

 near-by weed, stung it, malaxated it, and then carried it into the 

 burrow. Immediately she emerged with a caterpillar and flew 

 with it to the near-by field. She then continued to remove cater- 

 pillars from the nest until she had conveyed five to the field. In 

 all other cases the wasp carried the caterpillars afield as soon as 

 they had been dropped into the nest. It seems that the wasp is 

 averse to using caterpillars that have been captured by some other 

 wasp, and that she has some means of distinguishing them. 



To see if she could recognise her own captures, I frequently 

 removed the prey from a home-coming wasp and dropped it on the 

 ground among the nests. Invariably she would search until she 

 found the caterpillar and then would carry it to her nest. 



With a pair of forceps I occasionally attempted to remove the 

 caterpillar from a wasp tlwt was walking on the ground near her 

 nest. She would make strenuous efforts to retain her hold, occa- 

 sionally stinging the larva. If I succeeded in removing the cater- 

 pillar, the wasp would search for it until found and then store it 

 in her nest. 



Isely ('14, p. 294) states : " 0. dorsalis never seems to have any 

 difficulty in finding her way to her burrow after a field trip. Usu- 

 ally she flies directly to it ; I never saw her do otherwise when she 

 was returning from the field with prey. At times, when she re- 

 turned from the field unladen, I have seen her pause at another 

 burrow in the colony. This action may have been prompted by 

 curiosity instead of being a mistake in location." In that same 

 connection the Raus write ('18, p. 320) : "These wasps, when re- 



