PHOTIC EEACTIONS OF HONEY-BEE 345 



Dubois (p. 208) found that upon completely obscuring the 

 light from the prothoracic organ of one side of the body with a 

 covering of black wax, the beetle no longer crept in a straight 

 line. Smoked paper records, made in a dark room, showed that 

 such individuals crept in circles toward the functional eye. A 

 check experiment, moreover, showed that the results obtained 

 were not due to the weight of the wax. If instead of eliminating 

 one of the prothoracic organs, the cornea or the entire eye of one 

 side was destroyed with a red-hot needle (p. 211), very similar 

 results were obtained. When, however, both photogenic organs 

 of the prothorax were obscured or both eyes were destroyed, the 

 animal crept in a hesitant, irregular fashion, presently stopping 

 altogether. 



Dubois has interpreted these results from an anthropomorphic 

 viewpoint, as evidenced by his original paper and by a more 

 recent comment ('09). To the present writer, however, these 

 responses of Pyrophorus afford not only a typical case of circus 

 movements, but one of considerable theoretical importance as 

 well. The tendency to circle attendant upon the suppression of 

 one photogenic organ or the destruction of one eye may be attrib- 

 uted to the unequal stimulation on the two sides of the body. 

 If this be correct, the case is indeed unique, for the beetle is ori- 

 ented by its own luminosity. This, of course, in nowise affects 

 behavior in the normal animal. With a photogenic organ on 

 each side of the prothorax producing light of the same quality 

 and intensity, it is always perfectly oriented with respect to its 

 own light. But if the source of light or the photoreceptor of one 

 side be eliminated, the beetle promptly orients toward the oppo- 

 site side, the side which is receiving the greater stimulation. 



In recent years, a steadily increasing number of arthropods 

 have been shown to exhibit circus movements when one eye is 

 blackened or destroyed. The researches of Bethe ('97 a), Axen- 

 feld (^99), Holmes ('01, '05), Radl ('01, '03), Parker ('03), Had- 

 ley ('08), Carpenter ('08), Brundin ('13), Holmes and McGraw 

 ('13), Dolley ('16), and Garrey ('17), have demonstrated conclus- 

 ively that among phototropic arthropods generally, unilateral 

 photic stimulation results in a more or less asymmetric response. 



