hungerford: aquatic hemiptera. 109 



"A great similarity exists between some of the species of this genus, 

 and I have ventured to separate this species from the pallidum F., which 

 is said to have an elevated line on the thorax and another on the pectus 

 and postpectus. 



"The thorax on the posterior segment is generally obtusely tinged with 

 dull yellowish, with a blackish longitudinal line in the middle. 



"Var. a. Thoracic elevated line rather more obvious; grey lines of 

 the middle of the tergum more distinct. 



"Inhabits Mexico." 



Champion has given a much larger description in his Biol. Centr. Am. 

 Heteroptera, II, p. 145. 



Distribution : Quebec, Ontario, Maine, New Hampshire, Massachusetts, 

 Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Mary- 

 land, North Carolina, Georgia, Louisiana, Michigan, Illinois, Colorado, 

 Texas, New Mexico, Arizona, California and Oregon. 



GerHs orba Stal. 1859. 



Stal.-Fre?. Eugen. Resa. Ins., p. 264, 1859. 



Distribution : California, Oregon and Nevada. 

 Gerris conformis Uhl. 1878. 



Uhl., Proc. Boston Soc. Nat. Hist., vol. XIX, part IV, p. 435-436. 



"Dull olivaceo-fuscus, occasionally a little reddish-brown on the base 

 of the pronotum; form rather more slender than that of H. remigis; the 

 eyes more prominent. Pronotum invested with short, dense, olivaceous 

 pubescence, the middle line of anterior lobe impressed orange; the pos- 

 terior lobe coarsely, deeply, in places confluently punctured, with a slender 

 elevated longitudinal line running along the whole length; lateral edge 

 narrowly yellow. Antepectus pale yellow, powdered with white; under 

 sides of the anterior and intermediate cox« and outside of the posterior 

 coxas pale yellow. Medio and postpectus grayish sericeous. Hemelytra 

 blackish brown, not reaching to the top of the ante-genital segment; 

 tergum black, minutely, transversely wrinkled, the connexivum minutely 

 punctured, lateral raised margin yellow, the apical processes slender, 

 acuminate, as long as the segment to which they are attached. Venter 

 cinnereous, sericeous minutely pubescent, the posterior margin of the last 

 segment deeply concave, and together with the under side of the genital 

 segments rufescent. Male: Length to tip of venter, 15-16 mm.; greatest 

 breadth of pronotum, 2% mm. 



"The lateral mai-gin of pronotum has a stout ridge terminating in a 

 knob on the humerus, and between the humeri are two smaller protuber- 

 ances, which are sometimes obsolete." 



Distribution: Maine, Massachusetts, New York, New Jersey, Mary- 

 land, North Carolina, New Hampshire and Connecticut. 



Gen-is robusta Uhl. 1871. 



Uhler, Am. JI. Sci., ser. 3, I, p. 105, 1871. 



Distribution: Reported from California. 



Gerris gillettei, Leth. & Serv. 1896. 



Lethierry & Severin. Cot. Gen'l Heniip., vol. Ill, p. 60, (Xew name for L. productu-i Uhl.). 

 Baker, Hemiptera of Colorado Agri. Exp. Sta. Bull. 31, p. 61. 



"Larger and somewhat more robust than L. marginatiis Say, with 

 long, somewhat flattened, anal processes of a yellow color forming the 

 prolonged ends of the flat, broad connexivum, and is of the same color as 

 the last three segments. Color of the upper surface dark brown with a 



