1901.] NATURAL SCIENCES OF PIIILADELPIirA. 525 



next hour she made forty-six burden-bearing joui*neys through n, 

 returning forty-five times through ;; and once through e. She 

 undertook to carry in a larva larger than lierself and, after pro- 

 tracted and ineffective effort, dropped it at n:\ returned, and then 

 carried in a very small larva. On subsequent journeys she repeat- 

 edly passed over or close beside the dropped larva, but she seemed 

 to be aware that it had proven too heavy for her, and did not 

 renew her attempt to lift it. 



I then, during her absence in the nest, removed the earth over 

 a space of one centimeter from the floor at n"^, and washed the 

 glass floor and the neighboring walls and roof. On her return she 

 crossed the space unhesitatingly to the pupre pile at T, made two 

 burden-beariug journeys, one via c, one via a, with both returns 

 via n. She then came and examined the cleaned space, burrowed 

 in the bank at its sides, went to and fro several times over it, and 

 resumed her carrying in through this n run. 



Dot Four having first made without a burden excursions 

 through the 6, c, n, m and a runs, made fifty-five consecutive 

 burdeQ-bearing journeys, going in forty-five times by the a, twice 

 by the m, four times by the c-d, and four times by the n run. 

 Her returns were forty- nine times by the a, once by the m, twice 

 by the c, and three times by the n run. The b run was not again 

 entered. I then isolated her in a Petri cell, and tw'o days later, 

 having stopped the a run with plugs of cotton, I returned her to 

 the maze through T. She at once tried to enter a, pushing at the 

 cotton and endeavoring to creep under or over it. Finding it 

 impassible, she made several journeys through m. I then isolated 

 her two days more, unstopped «, and returned her to the maze 

 through T. She resumed her route through m, and made six 

 round trips by that run which she had used while a was stopped, 

 then she made a return through o, her older jDath, and from that 

 time all her ingoing journeys and returns were made by that route. 



Dot Five made sixty round trips, of which twenty-eight ingoing 

 journeys were made by the m, thirty-one by the a, and two by the 

 c-d run. Of her returns fifty-two w'ere made by c-d and nine, 

 at intervals, by m. When she had passed thirty-seven times 

 through m, I laid across its floor, at m^, while she was at T, a 

 strip of paper one centimeter wide. As soon as she reached it she 

 turned back with her burden and went in by c-d, returning as 



