208 



WILLIAM BRODBECK HERMS 



area into the darkness beyond, no further deflection took place. 

 The Hght pencil at the point of experimentation was about 2 mm. 

 in width, and individuals which had gained unusual headway 

 might rush, so to speak, through the light because of its narrow 

 proportions. The larvae usually paused on encountering the light 

 and made trial movements in a ver}^ striking manner, occasionally 



Fig-. 12 Lucilia caesar. Course of a larva that was creeping in a directive in- 

 tensity of about 0.5 C. M., when ungraded light of 70 C. M. was thrown upon it 

 from above. Orientation is clearlj^ influenced. 



Fig. 13 Course of a larva of Lucilia caesar when the light pencil is played 

 continuously on its head. 



Fig. 14 Lucilia caesar. Typical course of the larvae when encountering the 

 pencil of light. 



Fig. 15 Course of a larva of C. vomitoria showing the influence of the after- 

 effects of directive light. The individual was started under a directive intensity of 

 3 C. M. and crept in total darkness from X to Y, when a new directive intensity 

 of 0.56 C. M. was applied from in front. 



stretching the anterior segments so far that the darkness on the 

 other side was reached, when the larva continued on its way. 



The larvae of Lucilia caesar were not given as many trials, but ten 

 larvae, each given one trial for the right and one for the left 

 side, were deflected sharply each time as is illustrated by fig. 14. 

 This again bears out the conclusions that this species is more sensi- 

 tive to light than C. vomitoria. 



