INTRODUCTION. 



In the summer of 1910 the writer was a member of a 

 party which made an entomological survey of some fifteen 

 counties in northwestern Kansas. The field work was under 

 the immediate direction of F. X. Williams, while the collecting 

 and listing of the Heteroptera was assigned to the writer. It 

 was in this work that his interest was aroused in this group. 

 Thus, when the opportunity came to work upon some limno- 

 logical problem, under the direction of Dr. James G. Needham, 

 it was very happily arranged that a study of the biology and 

 ecology of the aquatic Hemiptera should be undertaken. 



There are some thirteen families of Heteroptera that main- 

 tain a more or less intimate connection with the water. The 

 Saldidae, Gelastocoridae, Ochteridse and Hebridae live upon the 

 shore. The Hydrometridse, Mesoveliidse, and some of the 

 Veliidse ( Micro velia, for instance) extend their range to the 

 floating mats of green algae and other plant rafts. The Gerridae 

 and some Veliidae course the surface of the waters. While 

 within the water dwell the Nepidae and Belostomatidae, which 

 keep a more or less constant contact with the surface, and 

 the Naucoridae, Notonectidae and Corixidae that dart here and 

 there through the water at will. 



Bound together by the ecological factor of environment and 

 relationship within an order, it has been the endeavor to treat, 

 'n the following pages, the habits, life histories, interrelations 

 and outside associations of the water bugs in such a way that 

 the result may be a finished thesis rather than a heterogeneous 

 collection of notes. This is a difficult task from the very 

 nature of the material treated. A glance at the table of con- 

 tents will indicate the general arrangement of subject matter. 



(8) 



