566 HYDRO.METRINA. 



reaching far beyond the points of the connexivum, the sides parallel, 

 the posterior margin rounded ; 2nd short, obtuse ; beneath brown, 

 1st and 2nd very conves, in length subequal, the sides parallel, with 

 a very narrow, projecting keel low on the sides ; 3rd very short, 

 obtuse ; ? above black ; 1st segment not reaching to the points of 

 the connexivum, flat, the sides hindwardly convergent, yellow ; 

 posterior margin straight ; 2nd short, narrowed posteriorly, apex 

 obtuse ; beneath, brown-yellow ; 1st in the middle sharply keeled, 

 the sides much flattened and depressed, but at the basal angles with 

 an abrupt, oblique elevation ; the 2ud as on the upper side. 



Length, 4^ — 5J lines. 



Common on stagnant and running water, from April to 

 September. 



Sjjecies 5. — HydrometrxV lacustris. 



CiMEx LACusTEis, Lhu P. S. 970 (1761); S. N. 732, 117 (1767). 

 Gerris — ScJmm. Beitr. 2, 43, 7, t. 3, fig. 11 (1832) ; Curt. B. E. 

 553, 5 (1835) ; II. Sc/if. Nom. Eut. 03 (1835) ; 

 Am. d Serv. Hem. 417, 2 (1813). 

 Hydrometra LACL'STRis, Bi'.rm. Handb. ii, 210, 2 (1835) ; H. Sclif. Waiiz. 

 ix, 68 &73, t. 301, fig. 930 (1850); Flor, 

 Ehyu. Liv. i, 742, 7 (1860); lieh. Europ. 

 Hem. 109, 10 (ISGl). 

 Gerris VARIABILIS, CuH. B. E, xii, 553, 4 (1835). 



Above brownish-black, dull ; liead, pronotum, and nerves of the 

 elytra with minute, golden, scale-like hairs ; beneath black with 

 a glossy, white pile, in certain lights with a brassy tinge ; the 

 abdomen of the $ in themiddle broadly yellow, with a central 

 black line. Antennce black ; 1st joint rather shorter than the 

 2nd 3rd and 4th together. Pronotiim rather strongly punc- 

 tured ; the 1st 5th strongly, roundly incrassated at the sides ; 

 the middle with a short yellow line, the undercurved sides with 

 an interrupted yellow line. T'ore-tliicjlis yellow-brown ; the 

 upper half above and beneath with a black line. 



13^ead rather strongly punctured; Face., on the sides, and the 

 antenniferous processes glossy, silvery-wliite. Antenncd black ; 1st 

 joint rather shorter than the 2nd 3rd and 4th together; 2ud and 

 4th in length subequal ; 5th longer than the 2nd. I^j/es black, 

 ehiaing. Ocelli obscure yellow. jRostnm black, the base yellow. 



