974 FAMILY XXXI. — GERRIDvE. 



found, but very rarely, fully winged, its common form being apterous. 

 The possession of wings always causes a change in the structure of the 

 thorax to accommodate the much enlarged muscles which the use of 

 organs of flight requires. These winged adults are generally found 

 solitary in the most unlikely places — isolated little pools, springs, rock- 

 holes, beach drift, far from the favorite haunts of this stream-loving 

 bug." 



1107 (1285). Gerris conformis Uhler, 1878, 435. 



Elongate, subparallel, more slender than remigis. Above a nearly 

 uniform fuscous-black; pronotum with a vague median line on front lobe, 

 the narrow lateral edge, sometimes the tip of hind lobe, and the narrow 

 edge of connexivum, dull yellow; under surface yellowish- or fuscous- 

 brown, usually thickly clothed with a very fine dense silvery-gray pubes- 

 cence; prosternum, coxa? and genital plates dull yellow. Antennae as in 

 remigis the joints more slender. Pronotum wider, with side margins of 

 basal third more oblique and hind margin more narrowly rounded; disk of 

 hind lobe densely punctate and with a distinct but low median carina 

 and a small glabrous nodule each side behind middle. Elytra entire, 

 reaching middle of sixth dorsal. Legs extremely long and slender, the 

 middle and hind femora longer than body. Sixth ventral of male very 

 broadly and shallowly concave. Length, 15 — 17 mm. 



Tuckerton, Pa., July (Gerhard). Charlotte and Swannanoa, 

 N. Car., April — June (Brimley) . Ranges from New England 

 west to Ohio and southwest in the coastwise states to North 

 Carolina. Bueno (1908a, 233) says that "it is very rare in the 

 north, but farther south, in the Carolinas, appears to be nearly 

 as common as remigis is with us." 



1108 ( — ). Gerris nebularis Drake & Hottes, 1925a, 70. 



Differs from conformis mainly by the character given in cc of key; 

 color and proportional length of antennals the same. Elytra in long- 

 winged form reaching base of first genital; in short-winged one only 

 to middle of second or third dorsal. Genital segments of male distinctly 

 broader than in conformis, the median ridge long and prominent with a 

 large, strongly depressed area each side. Length, 15.4 — 16 mm. 



Waltonville, III, July 20 (///. Nat. Hist. Surv. Coll.). Its re- 

 corded range extends from New Jersey west to Illinois and 

 south to Gainesville, Fla. 



1109 (1288). Gerris marginatus Say, 1832, 36; I, 362. 



Elongate, sides subparallel. Above dark reddish- or fuscous-brown, 

 thickly clothed with a fine yellowish pubescence; median line of front lobe 

 and narrow edge of hind lobe of pronotum and margins of abdomen dull 

 yellow; antenna? and legs reddish-brown, the front femora darker; 

 prosternum, coxa? and genital plates yellow. Antenna? short, stout, joint 

 1 but little longer than 4, 2 and 3 much shorter, subequal. Disk of hind 

 lobe of pronotum with a distinct median carina, the sides with a nodule 



