246 HETEROPTERA. 



6. (1). First antennal joint nearly equal to the remaining three taken 

 together, much longer than second and third ; antennae 

 almost as long as entire body ; hind femora twice as long 



as hind tibia Genus Metrobatos Uhler. 



(The one species thus far ascribed to this genus is M. hesperius 



Uhler.) 



Key to Genus Rheum atobates Bergroth. 

 Males. 



1. (2.) Hind femora and coxae curiously swollen and distorted. 



rileyi Bergr. 



2. (1.) Hind femora and coxae simple teimipes Meinert. 



Both Sexes. 



1. (2). Mesosternum yellow, unicolorous rileyi Berg. 



2. (1.) Mesosternum yellow with the anterior margin and the two 



posterior diverging bands brownish-black, these bands not 

 reaching to the posterior margin and dilated near the ante- 

 rior margin tenuipes Meinert. 



Gerris {Aquarius) reniigis Say; 1832, Descr. Het. Hem., p. — ; 

 1859, Compl. Writings, i, 362. 



The tables for subgenera and species will make the deter- 

 minatien of this form certain, but any doubt that might arise 

 can be at once set at rest by means of Thomas Say's original 

 description. This is perhaps the most common of our spe- 

 cies and one of the most widespread too, at least so far as 

 the area under discussion is concerned. It is to be found 

 most frequently on running waters, although it also frequents 

 still, but to a less extent. The winged form is very rare and 

 is seldom seen in collections. They congregate in groups in 

 shady, slow-moving parts of streams, at the tree roots pro- 

 jecting from banks into the water, in the shadow of bridges, 

 and in general in almost any place where they have some 

 shelter from the burning rays of the summer sun. They pass 

 the winter as adults, hibernating under boards or logs or in 

 other sheltered places near the waters they frequent. From 

 the earliest days of spring, as soon as the ice is melted, they 

 can be found in warm nooks and sheltered coves busily mat- 

 ing. The eggs are laid along the edges of grasses or other 

 leaves growing under water but near the surface, to which 

 they are fastened by a waterproof glue. They hatch out in 



