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 
Saldidz, Gelastocoridz, Ochteride and Hebride live upon the 
shore. The Hydrometridze, Mesoveliide, and some of the 
Veliidzee (Microvelia, for instance) extend their range to the 
floating mats of green alge and other plant rafts. The Gerridze 
and some Veliidz course the surface of the waters. While 
within the water dwell the Nepide and Belostomatidz, which 
keep a more or less constant contact with the surface, and 
the Naucoridx, Notonectide and Corixide 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, 
‘in 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) 
