UHLER ON INSECTS. 453 



Leugth scant 2 millimeters. Width of base of pronotum f millime- 

 ter. 

 A few specimens occurred on the margins of ponds west of Denver. 



Family HYGEOMETEID^. 



HYaHOTRECHUS St^l. 



S. remigis. 



Gerris remigis Say, Heteropt. New Harmony, 35, No. 1. 

 Collected by Dr. Packard, on July 10, in Denver; at Boulder, June 

 20 ; and at Manitou, July 15. It was found also by myself on the still 

 water along the margins of Sloan's Lake ; and it was very abundant 

 also on the surface of the irrigating canal proceeding from the caiion of 

 the Arkansas, in August. 



LiMNOTRECHUS St^l. 



L. marginatus. 



Gerris marginatus Say, Heteropt. New Harmony, 36, No. 2. 

 Dr. Packard collected specimens of it near Manitou, July 15. It was 

 seen by uie on the surface of puddles in the western suburbs of Denver, 

 in August. 



LiMNOPORUS Stal. 

 L . rvfoscutellatus. 



Gerris riifoscuteUata Lat., Gen. et Sp. Ins., iii, 134, No. 2. 

 It was collected by Dr. Packard, at Denver, July 28, and by myself 

 on the surface of small ponds and puddles in the depressions of the 

 plains west of Denver, August 8 and later. 



Family NOTONECTID^. 



isIOTONECTA Linn. 



1. X. insulata. 



Xotonecta insulata Kirby, Fauna Bor.-Amer., iv. 285, No. 399. 

 Noionecta riigosa Fieber, Kbyucbotog., 52, No. 7. 



This species was quite common in several pools of water standing in 

 hollows near the bed of creek on the outskirts of Denver, August 4 and 

 5. By the 18th of August, the inhabitants of these pools had gone, and 

 the pools essentially dried up. 



2. N. undulata. 



Notonecta undidaia Say, Heteropt. New Harmony, 39, No. 1. 



Found in the same pools as the precediug, and at the same time, but 

 much less abundant ; also in Sloan's Lake, west of Denver. Larva, 

 nymph, and imago likewise from the latter place, by Dr. Packard, 

 July 10. 



Family C0RISIDJ3. 



CoRixA, Geoff. 

 1. G. sutilis. 



Corixa sutilis Ubler, Bull. U. S. Gool. Surv., vol. ii. No. v, p. 73. 



A few specimens were met with in Sloan's Lake, on the highlands 

 west of Denver, August 5. 



