566 HYDROMETRINA. 



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

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

 1st and 2nd very convex, 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 2nd as on the upper side. 



Length, 4| 5J lines. 



Common on stagnant and running water, from April to 

 September. 



Species 5. HYDROMETRA LACUSTRIS. 



CIMEX LACUSTRIS, Lin. F. S. 970 (1761); S. N. 732, 117 (1767). 

 GERRIS Schum. Beitr. 2, 43, 7, t. 3, fig. 11 (1832) ; Curt. B. E. 

 553, 5 (1835) ; II. Schf. Nora. Ent. 03 (1835) ; 

 Am. et Serv. Hem. 417, 2 (1843). 



HYDROMETRA LACTJSTRIS, JBvrm. Handb. ii, 210, 2 (1835) ; H. ScJif. Wanz. 

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

 Rhyn. Liv. i, 742, 7 (I860); Fieb. Europ. 

 Hem. 109, 10 (1861). 

 GERRIS VARIABILIS, Curt. B. E. xii, 553, 4 (1835). 



Above brownish-black, dull ; head, 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 the middle broadly yellow, with a central 

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

 2nd 3rd and 4th together. Pronotum 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. Fore-thighs yellow-brown ; the 

 upper half above and beneath with a black line. 



Head rather strongly punctured; Face, on the sides, and the 

 antenniferous processes glossy, silvery- white. Antennas black ; 1st 

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

 4th in length subequal ; 5th longer than the 2nd. Eyes black, 

 shining. Ocelli obscure yellow. Rostrum black, the base yellow. 



