THE HOMING OF THE MUD-DAUBER. 22 3 



to near the top of upright C and then obHquely leftward and 

 upwards to the nest. The trip from window number one to the 

 nest consumed much less than a minute. 



Experiment i j} 



The same conditions as in experiment three. This experiment 

 was performed immediately after the close of experiment sixteen. 



The wasp on entering the room flew obliquely upwards, across 

 window number four, to the upper third of upright C\ then ob- 

 liquely leftward and upwards, across windows number four and 

 three, to a little beyond the upright A. It then searched about 

 until the nest was found. 



The shades were left in this condition from 10:4^ A. M. Jidy 

 ig to g A. M. Jtdy 20, at which time the wasp occasionally visited 

 the nest. The wasp on entering the room, flew obliquely up- 

 wards, across window number three, to the upper third of up- 

 right B ; then leftward, across window number three, to a little 

 beyond upright A, then obliquely rightward and upwards to the 

 nest. The conditions in this experiment and in experiments 

 three, five, seven, nine and eleven are identical, yet the behavior 

 in this case is quite unlike what it was in those. P.vidently pro- 

 longed exposure to the conditions described in experiment sixteen 

 has modified the behavior of the wasp. It had lost (forgotten) 

 its old response to the conditions described in experiment three 

 and been forced to acquire a new response. 



Conclusions. 



From these experiments it is evident that, in finding its w^ay 

 back to its nest, the mud-dauber is guided neither by what is 

 known as a homing instinct nor by w^hat Pieron has called a 

 kinesthetic reflex; for if either assumption were true, a manipu- 

 lation of the light should not have altered the wasp's behavior. 



Evidently light plays a prominent role in the homing of wasps, 

 yet the behavior of the mud-dauber is not a phototropism ; for in 



' This series of experiments was begun on the morning of July 17,1 908, and ended 

 on the morning of July 20, 1908. Experiments one to fifteen inclusive were performed 

 the first day and in the order mentioned. The intervals between the experiments 

 were only sufficiently long to permit the necessary adjustments to be made. Between 

 experiments fifteen and sixteen there was an intermission of almost two days ; between 

 experiments sixteen and seventeen, an intermission of five minutes. 



