110 THE UNIVERSITY SCIENCE BULLETIN. 



tinge of fuscous on the pronotum. Head of medium length, fuscous, cov- 

 ered with silvery, scaly pubescence on the lower sides and beneath. The 

 antennae short and stout, rusty brown, the second and third joints a little 

 thicker and darker at tip, the second shorter than the apical, but longer 

 than the third, the basal one a little longer than the superior line of 

 head, the fourth a little shorter, dark in color and tapering towards the 

 tip. Rostrum swollen at base, reaching a little behind the anterior coxiae, 

 with the tip black. Pronotum with the anterior lobe quadrangular and 

 flat, a very little shorter than wide, the anterior border a little thickened 

 and raised, the middle line behind this depressed and marked with a 

 short, yellow stripe, the posterior lobe evenly rounded off, a little flat- 

 tened, destitute of a carinate line, lateral margins narrowly yellow; 

 underside all silvery white. Legs of medium length, pale rusty beneath, 

 the posterior femora as long as from the base of posterior coxae to the 

 end of venter. Veins of corium prominent, two of the oval medio-apical 

 areoles pale. Sutures of connexivum pale, outer half of the connexivum 

 of the last three ventral segments including most of the segments them- 

 selves and the cerci, yellow, the middle line of venter with four indented 

 spots. 



"Length to end of anal segment, 10 mm. Width of pronotum, 2 mm. 

 A single female was sent to me from Colorado." 



Bueno in Ent. News, XXIV, page 21, has this to say about a female 

 specimen from Garfield, Utah, taken on brackish water. 



"This agrees in every particular with the original description and 

 with the type of the collection of the Colorado Agricultural Experiment 

 Station of Fort Collins, kindly loaned to me for study by Prof. C. P. 

 Gillette. This is the first authentic record of the species since it was 

 first described, and serves to establish its character as a good species. 

 Its chief superficial character separating it from Gerris (Limnotre chits) 

 marginatus Say, lies in the anal cerci, which in marginatus are short and 

 comparatively stout, while in gillettei they are long, attaining the ex- 

 tremity of the abdomen and comparatively slender." 



Distribution: Colorado, Utah, Montana, and California. — Van Duzee. 



Gerris marginatus Say 1832. 

 Say, Heter. N. Harm., p. 36; Compl. writings, Le Conte ed., vol. L, p. 362. 



"Thoras with an elevated line: behind with an obvious depressed 

 margin ; abdominal margin dull rufous. 



"Inhabits United States. 



"Body blackish, more or less tinged with olivaceous; thorax with a 

 raised line, more elevated behind; lateral indented edge dull rufous; 

 posterior depressed margin rather wide and very obvious; abdomen with 

 the margin dull rufous; feet dull rufous; anterior thighs with a blackish 

 line on both sides; coxae dull rufous beneath; beneath with a slightly 

 elevated line, terminating anteriorly in a depressed one; blackish, with a 

 silvery reflection. 



"Length over seven-twentieths of an inch. 



"Much smaller than the preceding {G. remigis) and more slender, of 

 a darker color; abdominal margin of a different color, and the posterior 

 margin of the thorax is broadly depressed. I obtained an individual, and 

 Nuttall gave (me) one which he tcok in Missouri." 



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

 Connecticut, New York, New Jersey, District of Columbia, Virginia, 

 North Carolina, Ohio, Michigan, Illinois, Missouri, Iowa, Kansas, Colo- 

 rado, Manitoba, Colifornia and Oregon. 



