978 FAMILY XXXI. — GERRID^E. 



with a low but distinct entire median carina, its sides feebly but evidently 

 diverging from apex to the nodulose humeral angles; thence strongly 

 converging and feebly reflexed to the narrowly rounded base. Elytra 

 reaching apex of sixth dorsal, rarely absent. Under surface with median 

 groove reaching metasternum. Length, 12 — 15 mm. 



Common on the smaller lakes of northern Indiana and in the 

 beach drift of Lake Michigan; not taken in the southern por- 

 tion (W.S.B.). Yaphank, N. Y., July 16 (Davis). It is a 

 palaearctic species occurring in northern Europe and Asia, and 

 in this country ranging from Quebec and New England west to 

 British Columbia and California and southwest to the moun- 

 tains of North Carolina. It is found on the still waters of ponds, 

 lakes and ditches, especially those in mountainous regions. 

 Drake states that it is very common about Cranberry Lake, 

 N. Y., where it is among the first of the water striders to ap- 

 pear in early spring. The eggs are deposited just beneath the 

 surface film of the water upon floating leaves of aquatic plants, 

 small sticks and other objects in the water. Bueno (1913, 109) 

 regards G. rufoscuteUatus as : 



"Without a doubt the Hemipteron of widest actual distribution next 

 to Nezara viridula (L.). It is known across northern Europe through 

 Siberia, thence to British Columbia and Oregon, ranging east to the 

 Northern Atlantic region. Here we have a form undeniably palaearctic 

 in origin, which has migrated from its native source and travelled 15,000 

 miles to found its colonies throughout the North Temperate Zone. Its 

 route has certainly been via Bering Straits into Alaska and thence east 

 and south. Its habitat and its predaceous nature have both contributed 

 largely to its fitness for this long voyage. It is furnished with good 

 wings, sucks any insect it can overcome and lives on the surface of the 

 water. It has therefore had an unimpeded and favorable route from the 

 land of its nativity eastward until stopped at the impassable barrier of 

 the Atlantic ocean." 



II. LlMNOGONUS Stal, 1868, 132 (Tenagogonus Stal). 



Our members of this genus differ from Gerris mainly by the 

 characters given in the generic key, and form a sort of connect- 

 ing link between that genus and the others of the family. In 

 the wingless forms they have the antennae long and slender, 

 about reaching hind coxae; eyes very feebly concave within; 

 pronotum with disk semicircular, much shorter than meso- 

 notum, the latter oval with hind margin broadly rounded ; abdo- 

 men shorter than remainder of body, its side margins above 

 flattened near base, obtusely carinate and inflexed toward apex ; 



