404 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [BuU. 



tions are for color characters, it is possible there are several species 

 confounded. 



Cheshire, 6 May, 191 1 (B. H. W.) ; New Canaan, 5 Sept., 1016 

 (M. P. Z.). 



Family NOTONECTIDAE. 



By J. R. DE LA TORRE-BUENO. 



These are the well-known back-swimmers, also called sometimes 

 boat-flies. All are aquatic and some species or other is sure to be 

 found in ponds or backwaters of slow streams, in the vegetation 

 close to the shore. Their chief peculiarity is that they swim upside 

 down, or upon their backs, mostly at or near the surface of the 

 water. The third pair of feet is thickly fringed with long hair 

 and used in swimming, except in Plea. All are carnivorous, feed- 

 ing on other insects, on young fish and on Entomostraca. They 

 are reported to be very troublesome in fish hatchery tanks. The 

 life history of three of our American forms is known. The 

 several groups of the family may be thus separated : 



Key to Subfamilies. 



Hind tibiae and tarsi ciliated, abdomen keeled, hairy, eyes very 

 large, conspicuous Notonectinae, p. 404 



Hind tibiae and tarsi apparently not ciliated, abdomen neither 

 keeled nor hairy, eyes small Pleinae, p. 407 



Subfamily Notonectinae. 



The subfamily Noloncctinae is the most important, as it contains 

 by far the greatest number of species and most of the genera. Of 

 the latter there are only two in the Eastern United States, 

 Notonecta and Buenoa, which may be distinguished thus : 



Key to Genera. 



Hemelytra pilose, hind tarsi without claws, last antennal joint much 

 shorter than preceding joint Notonecta, p. 404 



Hemelytra glabrous, hyaline, hind tarsi clawed, last segment of 

 antennae much longer than preceding joint Buenoa, p. 407 



Notonecta Linnaeus. 



Key to Species. 



1. Pure white, entirely black, or black and white 2 



Colored species, more or less marked with black _ 4 



2. Distance between eyes at front, not more than three times their 



distance at vertex ; pronotum about twice as wide as long 3 



Distance between eyes at front, six times their distance at vertex; 

 pronotum one and one-half times as wide as long, size 8-9 mm. 



raleighi 



3. Distance between eyes at front about twice their distance at vertex ; 



subrobust, size 10-13 mm undulata 



Distance between eyes at front about three times their distance at 

 vertex ; slender, white, often with faint black markings ; size 

 8-10 mm variabilis 



