Feb., 1920 Bulletin of the Brooklyn Entomological Society 5 



'jj it was several years, after I first became interested in the family 

 Gerridse, before I saw a water-strider fly without some artificial 

 stimulation. Flight occurs at dusk and during moonlight nights. 

 This fact I observed for the first time in Illinois. Flight may 

 take place at other times also, but it has not been seen by me. 



At this point it may be worth while to direct attention to some 

 of the statements, regarding flight responses of water-striders, 

 by certain other observers. Kirkaldy,* referring to the Gerridse 

 in general, states that the wings are used for no other purpose 

 except flight. This observer,'' discussing the flight of water bugs, 

 records the fact that night is their usual time for migration. 

 From the general context it is inferred also that water-striders 

 migrate at night. Although he does not say so specifically the 

 idea is presented that such migrations may occur during moon- 

 light nights. This writer^ directs attention to the fact that elec- 

 tric light, and other strong light, acts as a stimulation to migra- 

 tion, thus suggesting that such responses do not take place during 

 absolute darkness, but rather when there is a certain modicum 

 of light. This is in agreement with the fact that the water- 

 striders, Gerris orha Stal (Essenberg,'' p. 400), Gerris remigis, 

 and Gerris marginatus (Riley, MS.) are positively phototactic. 

 According to information from Kirkaldy,^ apparently, Gerris 

 thoracicus Schumm., in Hungary, and Gerris tristan Kirk., in 

 Ceylon, both may migrate at night. Referring to the Gerridse 

 in general, he^ (p. 151) makes the following statement, which 

 seems to indicate that this writer considers some of them to mi- 

 grate by flight : 



As has been previously remarked, many of the Gerridse con- 

 ceal themselves — in fact " hibernate " — under moss, stones, 

 _^-- etc., often far from water, during the winter. 



*Loc. cit., p. 109, footnote. 



5 Ibid., p. no. 



6 Ibid. 



■^ Essenberg, C, " The Habits of the Water-Strider, Gerris Remigis 

 t^J [^rba]," Journal Animal Behavior, Vol. V (1915), PP- 397-402. 



8 Loc. cit, p. no. 



9 Ibid., pp. 151-154- 



