THE PHOTIC REACTIONS OF SARCOPHAGID FLIES 183 



7 :30. The larvae had all returned to the flesh where they were 

 massed. Exactly when this return took place is not known. 



Experiment 7. July 24, 1907, 2.35 p.m. A total of about 350 

 migrated larvae were in the box. Of these an aggregation of 75 

 to 80 had collected in the upper corner of one end, and a larger 

 mass was collected in a lower corner on the end opposite and diag- 

 onal from the former aggregation away from the source of light 

 as far as possible under the conditions. Throwing the spectrum 

 on the larvae put the smaller mass in the red and orange bands, 

 and the larger in the blue end, practically under the ultra violet. 

 After ten minutes in this position no perceptible change in distri- 

 bution for the general masses was noticeable. 



2 :45. At this time the box was turned end for end which placed 

 the larger aggregation under the red and nearest the source of 

 light and the smaller under the blue. A very slow shifting of 

 both aggregations began, the larger mass gradually working away 

 from the front of the box to the farther side taking a diagonal 

 course, until that side was reached at 3:30. The animals in the 

 violet gradually moved out of this color through the blue into the 

 yellow and orange. At 3.30 they were distributed as follows: 

 9 on the bottom in the red, 16 on the face toward the light, 12 on 

 the back away from the light (in moving about some larvae 

 scattered so that there was a total of about 75 larvae moving 

 slowly at random in the entire blue end) ; all the remaining individ- 

 uals were in the red end, the mass lying in the yellow and orange 

 bands. 



3:45. Changing the box end for end again resulted in a rapid 

 and most marked movement away from the source of light, out of 

 the blue and green and into the yellow, orange and red, massing 

 under the yellow and orange as before. 



Experiment 8. July 25, 1907, 2:35 p.m. The migrated lar- 

 vae that had been used in Experiment 7, had collected with few 

 exceptions in a corner farthest away from the daylight. Casting 

 the spectrum on the box with the mass of larvae under the orange 

 and red caused comparatively little disturbance. Such individuals 

 as had collected in the opposite corner now in the violet, crawled 



