564 HYDROMETRINA. 



2nd pair of tibise ; tarsi ; 2nd pair, 1st joint twice as long as the 

 2nd ; 3rd pair, 1st joint 1^ time as long as the 2nd. 



Abdomen above dull black, the middle with a gray, posteriorly 

 widened, middle streak; Connexivum throughout, yellow outwardly, 

 posteriorly the colour occupies the entire breadth, the margin 

 brown. Underside black, with a slight silvery gloss, the middle with 

 a slight, depressed keel; the 6th segment posteriorly yellowish, 

 somewhat prominent at the sides; its posterior margin not very 

 deeply concave, but in the < with a large rounded excision in the 

 middle. Genital segments ; in the <$ extending much beyond the 

 points of the connexivum, beneath ochreous ; the 1st brown in the 

 middle, in the $ not extending much beyond the points of the 

 connexivum, sharp in the middle, the sides compressed, sloping 

 obliquely outwards, and with a deep oblique impression. 



Length, 4J 5J lines. 



Common on stagnant and running water from April to Sep- 

 tember. 



Species 4. HYDROMETRA GIBBIFERA. 



GERRIS GIBBIFERA, Schum. Beitr. 2, 41, 6,t. 3, figs. 57 (1832) ; //. Schf. 



Norn. Ent. 1, 62 (1835). 

 HYDROMETRA Fieb. Europ. Hem. 108, 9 (1861). 



Above brown-black ; beneath black with white or brassy lustre. 

 Antenna black or brown-black. Pronotum; anterior angles 

 with a rounded tubercle ; the middle next the anterior margin 

 with a short, thick, longitudinal yellow line ; the undercurved 

 side margins of the middle region only, yellow ; Metasternum 

 of the $ with a large orange tubercle. Anterior thighs black ; 

 on the basal J inwardly and beneath, yellow. 



Head punctured, the sides and the antenniferous tubercles glossy 

 yellowish-white ; Face ; central lobe at the end and the cheek-plates 

 yellow. Eyes and Ocelli black. Rostrum black, the base outwardly 

 yellow. 



Thorax. Pronotum deeply punctured, in the middle crenate, 

 the punctures obscured by the pilosity ; anterior angles with a 

 round, obtuse tubercle ; the 1st 5th very hollow on each side of the 

 keel, which is depressed, but a little raised in front, and with a short, 



