Ecological and Experunental Study of Sarcophagidce 49 



The presence of food is detected in a remarkably short time, 

 and this can only be accounted for on the assumption of a very 

 acute sense of smell. Comparatively fresh fish were exposed 

 w^here no flies were to be seen, and in ten or fifteen minutes many 

 flies were hovering about the food and some eggs had alreadv 

 been deposited. 



That the compound eyes so prominent in the Sarcophagidae are 

 of importance in orientation we are reasonably certain. If these 

 insects were deprived of their eyesight, food would probably be 

 found with difficulty. In several cases the eyes of Sarcophaga 

 sarraceniae were painted with india ink, affecting the flies in a 

 manner similar to that of animals whose semi-circular canals are 

 disturbed. Orientation was almost completely lost for a time. 

 On placing the individuals on their backs, they were barely able 

 to right themselves after frantically using both legs and wings. 

 They crawled about on the table in an aimless manner, or on the 

 writer's fingers. After a few minutes they flew slowly away, 

 buzzing noisily, passing over several pieces of fish placed on a 

 table. Their flight was directly toward a window, which they 

 struck with a thud. From this it would seem that the light was 

 not perfectly excluded. No doubt, much of the disturbance above 

 mentioned was due to the penetration of the india ink. 



It appears that the adults prefer the fresher food; fresh fish or 

 fish newly cast up being attacked more readily than those having 

 been allowed to dry. This is readily explained because of the 

 greater abundance of liquid food on the bodies of the fresher 

 specimens, and also because of the more pronounced ("fishy") 

 smell of such specimens. On several occasions a fish that had been 

 allowed to dry for a day or two was laid outside, and each time no 

 eggs nor larvae were deposited thereon, and the fish dried up in 

 the sun. Under natural conditions this would probably not 

 occur. 



Sarcophaga sarraceniae is rarely found in large numbers about 

 a carcass, while the screw-worm fly is most abundant nearer the 

 water and on larger carcasses. Lucilia caesar is found in the 

 majority on large or smaller carcasses farther away from the water 

 and on the small ones near the water. 



