400 



THE AMERICAN NATURALIST [Vol. LIII 



Attention lias been directed to some of tlie plij'sical con- 

 ditions that existed in a brook water-strider habitat in 

 the early stages of a drought. Certain features of such 

 a habitat in the later drought stages, will now be con- 

 sidered. So far as I am aware, there are no records in 

 the literature on aquatic Hemiptera, that describe the 

 responses of these gerrids, Gerris remigis, after the water 

 in their habitat actually disappears. The statements 

 given here are very condensed records taken, chiefly, 

 from my extensive field notes of the summer of 1911. 



Late in the summer a trip was made to White Heath for 

 the purpose of examining a number of isolated pools, on 

 the surface of which water-striders were trapped, in the 

 bed of the brook near that place. Particular attention 

 was directed to one pool in which the water had evapo- 

 rated rapidly during the previous week. It was exam- 

 ined about 8:00 a.m. and at that time the dimensions of 

 the pool were approximately 12 X 5 X i inches. It was 

 evident that the pool would be completely dry before 

 night. Evaporation was taking place rapidly, as the 

 atmosphere had been very dry for several days. The 

 heat had been intense for a number of weeks, a toni]tora- 

 ture of 90°-100° F. not being uncommon. 



2. Behavior in a Drying PooL— There were twentv gor- 

 rids trapped on the surface of the pool, already mentioned. 

 The insects did not move about very much on the water- 

 film. They were very quiet, frequently remaining, 

 practically, motionless for several consecutive minutes. 

 There was no behavior on the part of the hemipterons 

 that indicated any attempt to escape from the unfavor- 

 able surroundings. The members of this species being 

 hn-firlii apterous forms and tlnnr optimum habitat being 

 ])enn;inen! brooks and sti-eains (»t' moderate size, with a 

 cni-iTiit o!' medium xelocii v, it w;is, p<'rhaps, not strange 

 th.Ml thev ..\in.MMl no iv.pon.o. il,;,t showed definitely 



