No. 628] HABITAT RESPONSES OF WATER-STRIDER 411 



placed on the s^round one yai-d away fioni tlie water. 

 All those that got back to the water >ucc('r(l(Ml in reach- 

 ing the snrface-fihn in less llian (nic nmiutc. Similar 

 experiments were repeated for I'oiir ^iicco^ixc times, 

 using different individuals. Tliere was no cxpciMinciit in 

 which more than two gerrids failed to icacli tlic water. 

 Other exi>eriments were carried out in wliicli the water- 

 striders were placed two, tln-ec, and loui vai'ds away 

 from the stream. Tlie itiajoilt\ of tlie uvi-rids found 

 their way hack to the wnter. All tliox- tli;it were taken 

 two and three yards away trom the stream were ])ack 

 on the surface-fihn within 2 minutes and ;>() seconds. 

 Gerrids that were placed on the ground four yards away 

 from the brook evinced a few more random movements 

 tlian was tlie ease of tliose nearer to the water. A slightly 

 snialhM |)( icent,iiz( of t lie uei i i<I^ l'..niHl the wa\ hack to 

 the sti-eam rr..in tin- di-tance. Tlm-e water-t ri<lers that 

 reached the Hirfae,' uf the limck .li.l within four 

 minute. iVcni the time eaeli ex ) .ei'i uu'nt lu-an. 



; n<^/nn>^,^ (I Inn r<nnli,l Hith lhn.>l \ oi 

 expenuient- Wele pelf.M.iHd identleal to tliM-,. ..Il.ach 

 devriihe.l. except that the ater M i idei - we,,. pj.i.Ml en 

 a line with tlie long axis of their bodies paiallel with tii-^ 

 bank of the stream. It wa^ observed that the !iiai..iit> 

 of the o-errids were succe-f,,] in reachinu the watei. In 

 tlie ea-e of M.iiie individiiaK. a loimer time elap-e.i tliap 



theuatel -tli.lel- eithe, tllMle.iat e, i, e t ou a 1 d 1 1 le h, ook 



or elM'thex did m) a fe\\ -eeon-U afli-i tlii' liiM .oroientor 



jmiiped. for one yard or more, in the (hreetion in which 

 their heads were directe(h hel'ore tiiriiiim- toward thi' 

 l)iook. Some irerri(K weie place,! on the mnuixl f..nr 

 xar<N ,li-tai t fioni tl^. ^^^\r^. Ceitaiii in.h\i.lu.iN ,.t' 

 the-e exin.e.l !u- taiKx Ml piiiipini: .iu..-tK tou<,r.l 



theluonk aiKlthele w..,ea lllllllhe, . . f 1 a lldn , n n ,( .X m, en t 



/. U.^i.nn... WIni, r<,<,„n Ann , txnu />'/-^m/.. Other 

 expenineiit-. ol a character Hitiiiar to tlio>e that already 



