450 COLEOPTERA, 



convex, roughly sculptured, black insects, found at the mar- 

 gins of streams, on wet sand ; they cover themselves with a 

 mass of mud, so that no part of the insect is visible. Georys- 

 sus pusillus Lee. is our only species. 



Parnid^ MacLeay. These are aquatic beetles, having a 

 retractile head, and are often found clinging to submerged 

 stones, both in the larval and pupal states. The body of 

 the beetle is " clothed with a fine pu- 

 bescence, enabling a film of air to be 

 preserved beneath the water." The 

 larvae are hemispherical like a basin. 

 "The larva of Psephenus Lecontei 

 Hald. (Fig. 400, under side, enlarged 

 three times) is an elliptical object, 



l^ip* 4-01 



Fig. 400. with the margins widely extended be- 

 yond the body, and is seen on stones under the water of rapid 

 streams ; it is especially abundant in the rapids of Niagara, 

 and ditfers in no important particular from the larva of Heli- 

 chus of the next subfamil}^ It resjiires by branchial fila- 

 ments." (Leconte.) Elmis (Fig. 401, larva of a European 

 species) is known by the narrow, elongate scutellum. 



Heterocekid^e MacLeay. "This family consists of but a 

 single genus, Heterocerus ; it is represented in cA^ery portion 

 of our territory. The species are numerous, but very similar 

 in form and color, so that care is necessary in distinguishing 

 them. They are oblong or subelongate, oval, densely clothed 

 with short, silky pubescence, very finely punctuate, and of a 

 brown color, with the elytra usually variegated with undulating 

 bands or spots of a yellow color. They live in galleries 

 which they excavate in sand or mud at the margin of bodies 

 of water, and, when disturbed, run from their galleries and take 

 flight, after the manner of certain species of Bembidium." 

 (Leconte.) 



LuCANiD^ Latreille. This family is closely allied to the 

 next, and is often united witli it, as it differs chiefly from 

 ttie outer lamellate joints of the antennae not being so closely 



