PHENOMENA OF ORIENTATION EXHIBITED BY 



EPHEMERID/E. 1 



F. H. KRECKER. 



It is a well-known fact that in alighting Ephemeridsc orient 

 positively to a breeze. I became interested in this reaction and 

 the observations made naturally lead to others on reactions to 

 gravity and to light, and to the results of a conflict between any 

 of these three stimuli. 



The observations were made during the summer of 1915 at the 

 Lake Laboratory of Ohio State University at Cedar Point on 

 Lake Erie. Ephemeridse appear here in almost incredible 

 numbers. When a brood is at its height it is a very common 

 occurrence to find piles of the insects three or four feet square 

 and six to eight inches deep undenelectric lights. At a neighboring 

 amusement resort several carts were required each morning to 

 haul away the dead insects. The species with which the following 

 observations are especially concerned is Hexagenia variabilis. 

 The number, variety and arrangement of lights at the resort 

 presented favorably conditions for observing the reactions to light 

 of great numbers of individuals in what may be termed natural 

 surroundings. The equipment used for experiments with air 

 currents and gravity was simple and largely improvised. Never- 

 theless, since it is not primarily my purpose to measure intensity 

 of stimuli or rapidity of reaction, I believe the results obtained 

 have some interest and value. 



REACTIONS TO A CURRENT OF AIR. 



There was a question in my mind as to whether the positive 

 orientation of the Ephemeridee to a breeze is a response to the 

 breeze per se or whether other factors are concerned. In order 

 to test this I took a piece of glass tubing several inches long 

 and sent through it a weak but steady current of air so directed 



1 Contribution from the Department of Zoology and Entomology, Ohio State 

 University, No. 43. 



381 



