THE HOMING OF THE MUD-DAUBER. 



217 



Preliminary Observations. 

 These preliminary observations were made in a laboratory the 

 walls of which were ceiled with tongue-and-grooved pine boards. 

 These boards were arranged vertically. Two of the walls were 

 supplied with windows and two were not. Near the top of each 

 of these walls mud-daubers constructed nests. Some of these 

 nests were in dark places and some were in light places. I noticed 

 that the wasp never flew directly to the nest, but that it would 

 alight on a certain crack. After ascending, afoot, this crack, 

 until it had reached the height of the nest, it would turn and walk 

 to it. The same wasp always alighted on the same crack and 

 at about the same distance from the floor. This led me to sup- 

 pose that wasps used the cracks as landmarks. In this room a 

 certain window was lowered from the top, through which open- 

 ing the wasps came and departed. In another room, in which 

 similar experiments were conducted, the window was raised from 

 the bottom. Wasps frequented this room as much as they did 

 the other. Evidently wasps can learn the way into a room by 

 either a high or a low opening. 



The Environment of the Experiments. 

 This series of experiments was performed in a laboratory thirty- 

 seven and a half feet long, twenty-five feet wide and twelve feet 



P'iG. I. This is a diagram of the room arranged for experiment one. 1-6, win- 

 dows ; A-E, upright facings of windows ; a, location of the nest. The wood-work 

 of the windows is shaded with broken lines, the window-shades with dots. The 

 boards in the floor, ceiling and dado are drawn twice as wide as they were. 



high (Fig. i) which was situated in the third story of a large 

 brick building. The ceiling was covered with tongue-and-grooved 

 pine boards and a four-foot dado of pine ceiling extended around 



