518 WILLIAM L. DOLLEY, JE. 



of 1 per second than it does in continuous light. That inter- 

 mittent light of a certain frequency of interruption acts as a 

 stimulus upon Vanessa indicates that orientation in light in this 

 butterfly may be due to the time rate of change of intensity. 



I wish to express my very sincere appreciation of the kind 

 interest, numerous suggestions, and unfailing aid of Prof. S. 0. 

 Mast in this work. It is a pleasure also to acknowledge my 

 indebtedness to Dr. H. E. Howe for the loan of apparatus and to 

 my brother, S. B. Dolley, and my student, W. A. Wightman, for 

 valuable assistance in conducting the experiments. 



SUMMARY 



Vanessa antiopa does not move faster in strong light than in 

 weak but on the contrary tends to move faster in weak light 

 than in strong, if the difference between these illuminations is 

 sufficiently great. This behavior is not in accord with that 

 which is demanded by Loeb's "continuous action theory" of 

 orientation. The results in general support those described in 

 an earlier paper which indicated that orientation of Vanessa 

 in light can not be accounted for on the basis of Loeb's theory. 



Vanessa moves faster in intermittent light of a frequency of 

 interruption of 10 and 16 per second than it does in continuous 

 light. This supports the contention that orientation in light 

 in the mourning-cloak butterfly is due to the time rate of change 

 of intensity. 



BIBLIOGRAPHY 



Dolley, W. L., Jr. 1916 Reactions to light in Vanessa antiopa, with special 



reference to circus movements. Jour. Exp. Zool., vol. 20, pp. 357-420. 

 EwALD, W. E. 1914 Versuche zur Analyse der Licht- und Farbenreaktionen 



eines Wirbellosen (Daphnia pulex). Zeitsch. f. Sinnesphysiol., Bd. 



48, pp. 285-324. 

 LoEB, J. 1912 The mechanistic conception of life. Chicago, pp. 227. 

 Mast, S. O. 1911 Light and the behavior of organisms. New York, pp. 378. 

 Parker, G. H. 1903 The phototropism of the mourning-cloak butterfly. 



Mark Anniversary Volume, pp. 453-469. 



