410 



THE AMERICAN NATURALIST 



[Vol. Llir 



After having observed the erratic, aimless character of 

 the responses of these insects, Gerris remigis, their ability 

 to reach some other distant body of water appeared doubt- 

 ful, and very ]arg:ely de])endent upon chance. If a larger 

 body of water should he very near to the haunts of the 

 gerrids, tlu'ii tlici e would he, through their random jour- 

 neys, a greater ])ossihility of reaching such a situation. 

 In any case, their responses appear to be responses of 

 repeated trial and failure, until through many repeti- 

 tions, some gerrids eventually reach the water. 



III. EXPEKIMENTS IN CONNECTION -WITH BeOOK IIaBITAT 



AT White Heath 

 1. Methods. — I now wish to record certain other ob- 

 servations, on the responses of Gerris remigis, of a some- 

 what different character from those that already have 

 been discussed. Many times when out in the field collect- 

 ing Gerris remigis, some water-striders escaped while I 

 was picking them out of the net as it lay on the ground 

 near the margin of the stream. I noticed that these indi- 

 viduals generally found their w^ay back on to the surface 

 of the water. Several times it occurred to me to under- 

 take a series of experiments with these water-striders for 

 the purpose of discovering their ability to return to their 

 own habitat after having })een remoVed from it. The 

 l)lan was to plaee tlietii on the uroniid at various di-tauces 

 away from the stream and ol)-ei-\-e whether oi' not they re- 

 turned to the water, ajid if so to record the readines> with 

 which this was done. Up to the present, the experi- 

 mental w^ork has not yet been carried out as extensively 

 as w^as desired, but the results that have been olitained 

 may be of interest. The experiments were undertaken 

 at tlie brook near White Heath, that has he.Mi nu^nt ion.'-l 

 previously. The site selected was at a l)laee where the 

 bank was flat, with its surface raised onlv a few inches 

 ahovr that (.f the water. 



■!. lirspni,srs Win „ Farinf/ //rooA'.— Twcuty gcrrids 

 with tlieii- head- turned directly toward the stream, were 



