PHOTIC EEACTIONS OF HONEY-BEE 397 



to that exerted by natural asymmetry, many failures to turn 

 toward the functional eye are probably thus accounted for. 



/. Modifiability through experience. The work of Axenfeld, 

 Holmes, Brundin, and Dolley has shown that a number of ar- 

 thropods are able to modify their photic behavior through expe- 

 rience. The same is true of the honey-bee, at least in directive 

 light, as the following experiment shows. Each of a number of 

 normal bees, selected on the basis of the accuracy with which they 

 oriented to directive light, had one eye blackened. On the fol- 

 lowing day those animals which exhibited a more or less pro- 

 nounced tendency to loop toward the functional eye were sub- 

 jected to trials (twenty to twenty-five in number) in the directive 

 light area. 



Bees which displayed little or no tendency to loop were given 

 several trials to ascertain if their behavior was constant, and then 

 discarded. These animals may have been able to modify their 

 behavior almost immediately, or their failure to exhibit circus 

 movements may have been due to an imperfect covering of the 

 eye, or to the effect of contact stimulus. 



Of those bees which did perform circus movements, records 

 were taken about every ten to twenty minutes from 9 a.m. to 

 5 P.M., with the exception of about an hour at noon. Ten bees 

 were thus tested. Four of these animals displayed a steady and 

 marked improvement in the course of the trials. Two others 

 showed some improvement, although considerably less than the 

 first four. Two more of the ten improved for a time, only to 

 regress again, so that while a number of trials near the middle of 

 the series were somewhat modified, those at either end were 

 much alike in the number of loops performed. The last two bees 

 showed practically no improvement, although in one of the ani- 

 mals the tendency to circle was at no time very pronounced. It 

 is quite certain, therefore, that at least some bees are able to mod- 

 ify their responses to directive light through experience . 



The records shown in figure 17 afford a striking example of this 

 modifiability. Although in its first trials the animal looped re- 

 peatedly as it crept toward the light, it was subsequently able to 

 reach the light by a nearly straight course. This animal, how- 



