Insects, etc., of Caledonia Creek. 83 



from their six long legs branching out from their small bodies, and their peculiar 

 motion, in jerking over the surface of the water of ponds and the more quiet 

 portions of our streams, are familiar to all. The popular name of water-boat- 

 men is sometimes applied to them. They are extremely active creatures, skim- 

 ming about with great velocity, and quickly turning in any direction. West- 

 wood states that their hind feet act conjointly as a rudder, while the longer 

 middle feet, placed at the middle of the sides of the body, are used somewhat 

 as oars ; they are not, however, dipped into, but merely brush along, the surface 

 of the water. With their shorter fore-legs they seize and hold the small insects 

 upon which they prey, while devouring them. The under-side of the body is 

 covered with a plush-like coating to repel the water. 



They belong to the family of Hydrometridce, and are placed by Latreille in 

 the section of Ploteres — not very appropriately named, as Westwood remarks, 

 for their motion is not that of swimming. For a long time the generic name of 

 Gerris has been applied to them, but they have been recently referred to new 

 genera by Stal. Professor Grlover* cites six species, viz. ; G. caniculatus Say 

 (G-eorgia), G. conformis Uhler (Md.), G. lacustris Fabr. (Md.), G. rnarginata 

 Say (U. S.), G. remiges Say (U. S. generally), and G. rufoscutellata Latr. 

 (U. S.). The last three species have a broad distribution, they having been 

 collected by Prof. Uhler and Dr. Packard, in Colorado.! Of G. remiges, 

 Prof. Uhler writes, loc. cit. : " 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 canon 

 of the Arkansas, in August." Prof. Uhler, to whom I owe the authoritative 

 determination of this species, refers it to the genus Hygrotrechus of Stal. 



Numerous examples of another form of " water boatman," of the family of 

 NotomrtidcB, and of the genus Corlxa, were contained in the box of Chara 

 received from Caledonia in February. They are apparently of two species — 

 the larger measuring three-eighths of an inch in length of abdomen, and the 

 smaller about one-half so long. They were submitted to Prof. Uhler, who 

 informs me that " the species does conform to any published description, and 

 is, therefore, probably undescribed." From an accompanying pen-and-ink 

 sketch, the larger form shown in fig. 11 of plate 4, is undoubtedly the one re- 

 ferred to, the smaller one having probably escaped from the box in which they 

 were sent alive . 



Large companies of these insects are often seen floating on the surface of the 

 water, frequently with their back downward. When disturbed, they dive to 

 the bottom with a quick, paddling motion. Their hind legs have the two tarsal 

 joints very long, broad, and fringed with cilia, admirably adapting them for 

 swimming purposes. The fore-legs are partly prehensile, armed with a single 

 claw — these legs not seen when at rest. The middle legs are comparatively 

 slight, terminating in a long aud slender claw ; when floating on the surface, 

 these are bent backward, while the hinder legs are thrown forward as balancers, 

 as shown in the figure, apparently reversing their true position. 



A species of this genus, C. ?nercenaria Say, is said, by ^ay, to be largely 

 used in Mexico as food. 



In figure 8 of plate 4, the family of Belostomidas is represented, in Belostoma 

 Amerlcanum Leidy ; the specimen figured is not of the maximum size. The 

 largest of the Caledonia examples measured two and a quarter inches in length of 



♦Manuscript Notes from my Journal. Order Hemiptera. By Townend Glover, p. 39. 1876. 

 t Bulletin of the U. S. Geolog. and Geograph. Survey of the Terr. Vol. iii, No. 2, p. 453. 1877. 



