THE CANADIAN ENTOMOLOGIST. 33 



NOTES ON THE POSITIVE HYDROTROPISM OF GERRIS 



MARGINATUS SAY AND DINEUTES 



ASSIMILIS AUBE. 



BY HARRY B. WEISS, NEW BRUNSWICK, X.J. 



Wingless forms of Gerris marginat'us, which is quite common 

 throughout New Jersey, when removed from a pond containing 

 some three thousand square feet of water and liberated at distances 

 of one, two, three, four, five, six, seven, eight, and nine yards from 

 the water, immediately made their way back to the water without 

 hesitancy. Of course their movements, which consisted of a 

 series of jumps, were more or less clumsy, but all started in the 

 right direction even though purposely headed the wrong way. 



When liberated at a distance of ten yards, they had some 

 slight trouble in getting their bearings, but after making several 

 false starts, finally wound up by going in the direction of the water. 

 At a distance of fifteen yards, a longer time and more moving 

 around were required before the right direction was located. At 

 thirty and forty yards away, they seemed to lose their bearings 

 completely and moved aimlessly about in all directions. Even 

 at the end of an hour they were no nearer the water. 



The actions of Dineutes assimilis, which is also quite common 

 in New Jersey, were somewhat more interesting. These beetles, 

 when liberated three or four feet from the water, scrambled back 

 with difficulty owing to the character of their legs, which were not 

 meant for locomotion on land. 



At nine or ten feet from the water, after trying rather akwardly 



to walk back, they rose to a height of ten or twelve feet and flew 



towards the pond, both with and against a slight breeze. At 



75 feet from the water, they walked in all directions and then rose 



'in irregular circles to a height of 30 feet and flew to the pond. 



On several occasions, when a brisk wind was blowing from the 

 direction of the water, they were carried inland in spite of heroic 

 attempts to fly against it. When liberated at a quarter of a mile 

 from the water, after an aimless existence on the ground for half a 



January, 1914 



