GYRINIDJL GYRINUS. 95 



municate with the tracheae by means of a small air tube; the last 

 joint of the body is very small, and terminates in four long parallel 

 hooks : they live in the water, and towards the middle of summer 

 prepare an oval coccoon, pointed at each end, resembling brown 

 paper, and fixed to the leaves or roots of plants. 



Genus XC. — Gyrinus Auctorum. 



Palpi, external maxillary with the three first joints small, the terminal large, 

 ovate ; internal uniarticulate : labrum short, transverse, sometimes projecting, 

 ciliated anteriorly : mandibles short, bifid at the apex : mentum large, bilobed. 

 Antennae with the basal joint large, globose, produced externally in a trian- 

 gular compressed lobe, the remaining joints forming the club : head trigonate : 

 body convex: elytra generally covering the abdomen entirely: anterior tarsi 

 of the males dilated. 



The short, rigid antenna?, and elongate anterior legs sufficiently 

 distinguish the indigenous Gyrini from the other Hydradephaga ; 

 but the genus as now constituted evidently contains two dissimilar 

 forms ; the first comprising those species which have the labrum 

 short, the body moderately convex, very glossy, striated and naked, 

 its apex projecting semicircularly beyond the elytra, and the latter 

 sub truncate ; the others have the labrum projecting, the body very 

 convex, punctured, and villose, with its apex not produced beyond 

 the elytra, but somewhat pointed ; the former appear to be more 

 gregarious than the latter, and may be observed during fine weather 

 upon the surface of the water in clusters, rapidly whirling about 

 in all directions, whence their names of water-flea or whirl-wig : 

 sometimes they are motionless, but upon the approach of any one 

 they are instantly in motion again, and if alarmed dive quickly, 

 carrying with them a bubble of air, resembling a globule of quick- 

 silver : in the evening or in dull and cold weather they are rarely 

 to be seen, being at such times sheltered under the banks, or be- 

 neath the roots of plants. They seize their prey by means of their 

 elongate anterior legs ; many of the species secrete a fluid of a most 

 disagreeable odour, which they eject when handled, and the scent 

 will remain for some time on the fingers. 



A. Elytra glabrous, punctate-striated. 

 Sp. 1. aeneus. Oblongo-ovatus, caeruleo-niger nitidissimus, subtits obscure aniens, 



capite, thoracis elytrorumque limbo et margine rejlexo suturdque nitido-ceneis. 



(Long. corp. 3— 3^ lin.) 

 Gy. aeneus. Leach MSS.—Steph. Catal. p. 53. No. 537. 

 Oblong-ovate, very glossy blue-black : head brassy, very smooth, with two im- 



