Feb., 1920 Bulletin of the Brooklyn Entomological Society 7 



The species is a strong flier, and I have found it in ocean 

 beach drift in July, on the shores of Long Island. 



O7 The following quotatioii/'from him^^^ gives a little more informa- 

 tion with reference to the flight of water-striders, particularly 

 those that live on the surface of stagnant waters : 



The species inhabiting land-locked bodies of water must, 

 however, always have some means of travelling if the water on 

 which they live dries up, as so frequently happens with small 

 ponds or water-holes. Hence wings still normally persist in 

 these forms. 



During such droughts as have been mentioned, I have ob- 

 served in the prairie regions of Illinois, after intermittent brooks 

 have reached the isolated pool stage, that, not infrequently, evap- 

 oration proceeds rapidly, and these pools become very contracted. 

 When they become so small that they are not more than one or 

 two feet in diameter and only two or three inches deep, I have 

 found that usually the number of alate specimens of Gerris mar- 

 ginatus are very few, and on some of these small pools, there are 

 no individuals of this species present. This fact seems to indi- 

 cate that many of them have migrated, probably^ by flight. On ^/ 

 the surface of these very small pools of water, Gerris remigis is 

 present in large numbers, but, strange to relate, this species 

 evinces no responses which seem to indicate an attempt to escape 

 from such unfavorable surroundings. This is a phenomenon to 

 which P^ have directed attention in another of my papers. 



Eventually, many of these small isolated pools become com- 

 pletely dry. As Kirkaldy'-® has suggested, large numbers of 

 apterous gerrids must perish, and in those instances where a 

 cy species is represented, in a particular locality^ by apterous indi- (yj 

 viduals only, it may become extinct, in so far as that particu- cJy 

 lar region is concerned. The latter contingency would be the 

 result should the drought be protracted, severe, and extended 

 throughout a large area. During such periods of drought, I am 



16 Ibid., p. 297. 

 ''-'^ Loc. cit., p. 400. 

 18 Loc. cit, p. 109. 



