370 S. J. HOLMES AND K. W. McGRAW 



subsequent trials the turns were toward the left in every case. 

 In one experiment with a skipper butterfly with the right eye 

 blackened there were circus movements to the right in nine 

 out of ten trials. With another specimen of the same species 

 there were circus movements toward the blinded side in six out 

 of seven trials. In another specimen there were circus move- 

 ments toward the blinded side in all of the six trials that were 

 made. The cause of the turning toward the blinded side was 

 not carefully investigated. Ordinarily this species of skipper 

 shows a positive, although somewhat spasmodic positive photo- 

 taxis. Like some of the butterflies studied by Radl 3 and Parker 4 

 it shows a tendency to orient negatively when basking in strong 

 sunlight. Possibly the circus movements of the skippers toward 

 the blinded side may be associated with this trait of negative 

 orientation when at rest in a strongly illuminated region. Experi- 

 ments with two specimens of Melitcsa chalcedon with the right 

 eye blackened over showed circus movements to the left in 

 thirty successive trials in each case. After a half -hour's interval 

 each specimen made ten circus movements to the left. 



Two specimens of the fly Tachina with one eye blackened 

 over showed very decided circus movements toward the normal 

 side in each of twenty -five trials. The body was held leaning 

 over toward the normal side and the insects showed a tendency 

 to roll over toward that side. A specimen of Eristalis tenax 

 showed circus movements toward the normal side in thirty 

 successive trials, and a tendency to lean over toward the normal 

 side. Several other experiments with other flies gave very sim- 

 ilar results. The tendency to hold the head and body tilted 

 over toward the normal side is very noticeable in several species 

 of Diptera that were previously observed in an ordinary environ- 

 ment. . It was especially marked in a species of robber fly, 

 Asilus, which when at rest leaned over so strongly toward that 

 side that in its attempts at locomotion, which eventuated in the 

 usual circus movements, it would continually fall over. The 

 light in this case seemed to exercise a strong, continuous and 

 almost uncontrollable effect on the tonus of the muscles. 



It was observed by one of the writers that Ranatras when 



3 Radl, E. Untersuchungen iiber den Phototropismus des Tiere. Leipzig. 1903. 



4 Parker, G. H. Phototropism of the mourning-cloak butterfly, Vanessa antiopa 

 linn, Mark Anniversary Volume, pp. 453-469. 1903. 



