Uhler.] 436 [April 17, 



Dull olivaceo-fuscous, occasionally a little reddish brown on the 

 base of the pronotum ; form rather more slender than that of H. remi- 

 gis ; the eyes more prominent. Pronotum invested with short, dense, 

 olivaceous pubescence, the middle line of anterior lobe impressed, 

 orange; the posterior 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 inter- 

 mediate coxae and outside of the posterior coxse pale yellow. Medio- 

 and pdstpectus grayish sericeous.. Hemelytra blackish brown, not 

 reaching to the top of the ante-genital segment; tergum black, mi- 

 nutely, 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 cinereous, 

 sericeous minutely pubescent, the posterior margin of the last segment 

 deeply concave, and together with the under side of the genital seg- 

 ments rufescent. Male. Length to tip of venter, 15-16 millims. 

 Greatest breadth of pronotum, 2| millims. 



The lateral margin of pronotum has a stout ridge terminating in a 

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

 tuberances, which are sometimes obsolete. 



No. 14, Harris' Collection, e?. "September 20, 1821. Charles 

 River." 



A fully winged male is the only specimen in this collection. The 

 other specimen with the same number is the female of H. remigis Say. 

 This species was formerly very common on the streams near Balti- 

 more, but it is now seldom met with ; it occurs in summer. 



LlMNOTRECHUS Stal. 



L. marginatus. 



Gems marginatus Say, Hemipt. New Harm., 36, 2. 



No. 29, Harris' Collection. " Gerris humilis Say, MSS., so named 

 by himself. Water, July 20, 1827, May 15, 1826, and Maine, Mr. 

 Randall, April and May." 



It seems strange that Dr. Harris did not recognize in this the Gerris 

 marginatus Say. It agrees in all respects with the description of that 

 insect and the size there given will hardly apply to any other of our 

 species. Although offering slight differences of color and form, it 

 comes very near to L. lacustris Linn, of Europe, and it may yet prove 

 to be but a local, or climatic form of that species. One male and 

 two females now belong to the collection. 



