OnBEu5. COLEOPTERA. 505 



new. ser. vol. ii. and iv. ; and still more recently by M. Auljo in his continuation of the Species genera, 

 des Colioptei-es of Dejean, and in the Cole'opteres cTEuropc. In the former of these two works, pub 

 lished in ] 83S, he divides the 1 lydrocanthari into three groups, HalipUdes, Dythcidcs, and Ilijdroplorides ; 

 the first comprises two genera, Ifaliplus, 20 sp. ; and Cnnmidutus, 3 sp. : the Dytiscidcs arc divided into 

 Pcelobius, 1 sp. ; Cybister, 3G sp. ; Dytiscus, 17 sp. ; Eunectes, 1 sp. ; Acilius, 17 sp. ; Hydaticus (in four 

 sections), 44 sp. ; Cohjmhetes, 39 sp. ; Ilybius, 11 sp. ; Ayabus, GO sp. ; Ccpelatus, 17 sp. ; Malus. 1 sp. ; 

 Coptotoma, 1 sp. ; Anisomera, 1 sp. ; Notcrus, 3 sp. ; Ilydrocanthus, 7 sp. ; Suphis, 1 sp. ; Laccophilus, 

 22 sp. ; and the Hydroporides comprise the genera Celiiia, 3 sp. ; Vatellus, 1 sp. ; Hyphydrus, 1 1 sp. ; and 

 Hydropo}'us, 122 sp. Besides these, Mr. Babiugton has read the descriptions of the species brought 

 home by Mr. C. Darwin in a paper before the Entomological Society of London.] 

 The second principal genus, that of 



Gyrinus, Linn., — 

 Comprises those which have the antennae in a mass, and shorter than the head ; the two fore-legs are 

 long, advanced like arms, and the four others very short and depressed, broader and oar-like. The eyes 

 are four in number, the body is oval, and generally very shining; the antennae, inserted in a cavity before 

 the eyes, have the second joint exteriorly elongated like an ear, and the following joints (of which 

 seven are only distinctly visible) very short, and closely united into a mass nearly like a spindle, and 

 rather bent ; the head is inserted into the thorax as far as the eyes, which are large, and divided by a 

 ridge on the sides, so that there appear two above and two below ; the upper lip is rounded, and very 

 much cihated in front ; the palpi are very small, and the inner pair of the maxillary are wanting in many 

 species, especially the large exotic ones. The thorax is short and transverse, the elytra are obtuse or 

 truncated at the posterior extremity, leaving the anus exposed, which is terminated by a point. The 

 two fore-legs are slender, long, folded up, and held nearly at right angles w ith the body when shut up, 

 and terminated by a very short compressed tarsus, of which the under-side is clothed with fine plush in 

 the males. The four other feet are broad, very thin like membrane, and the joints of the tarsi form 

 small leaves. 



These insects [which are called Whirlwigs, from their peculiar motions] are in general of small or 

 but moderate size. They are to be seen, from the first fine days of spring till the end of the autumn, 

 on the surface of quiet waters, and even upon that of the sea, often assembled in great numbers, and 

 appearing like brilliant points. They swim or run about with extreme agility, curvetting in a circular 

 or oblique, or indeed in every direction : whence their ordinary French name of Tourniquets, or their 

 English name given above. Sometimes they remain stationary without the slightest motion ; but no 

 sooner are they approached than they escape by darting under the surface of the water, and swimming 

 off with the greatest agility. The four hind-legs are used as oars, and the fore ones lor seizing the 

 jirey. Ordinarily stationed upon the surface of the water, the upper side of the body is always dry ; 

 and when they dart down, a bubble of air like a silvery ball remains attached to the hind part of the 

 body. When seized, they discharge a milky fluid, which spreads over the body, and probably produces 

 the disagreeable odour which they then emit, and which lasts a long time upon the fingers. Some- 

 times they remain at the bottom, holding upon plants, where also they possibly hide themselves 

 through the winter. 



Gyrhnts natator, Linn., is three lines lon^, oval, very smooth and shining, of a bronzed black 

 colour above, black beneath, with the legs fulvous ; scutellura triangular, and very pointed ; elytra 

 with small impressed dots in regular longitudinal lines. The larva is long and linear, 13-jointed, 



I4^--'.'1 ■'•■^ each of the first three segments supporting a pair of feet; the fourth and following segments have 

 X\\\\ ;'';; L on each side a conical membranous filament, flexible, and bearded at the sides ; tbe twelfth seg- 

 J\ '■„ ;. ;. A pigjjj. jjgg fg^,.^ ijyf tj-jpy jjj.g loiigpr^ a^^\ ^jgnt baclcwards. This larva lives in the water, coming 

 forth at the beginning of August to undergo its changes. It forms a cocoon of an oval form 

 pointed at each end, which it afllxes to rushes. This is a very abundant species [throughout 



Figr.SG.-Gyrir.us ' 



natal or. EurOpS.J 



[Messrs. Laporte, Brulle, and Aub<5, have especially studied this family, and have proposed several additional 

 genera. The last of these authors, in his Species General above mentioned, has described the following genera: 

 i\aime]y,—E)ihyt{rus with three species, Gyrinus with forty-five, Patrus with one, OrectocMlus with fourteen, 

 Cyretes with eight, Porrorhynchns with one, and Dineutes with twenty-one.] 



