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Show 11\SJ<~CT A. ne1·ally small, unequal, and unid• entated inferiorly. The scutel\u m is tolerably laq~e. These spec1es compose the genus , HvnROPHILus, Geoff. Fab. Leach.-Dytiscus, Lin. Here the sternal spine is strongly prolonged behind. The last joint of the two anterior tarsi of the males is dilated in the form of a triangular palette. The scutellum is large. They form the Hy. drous ofM. Leach(l). The Jarvre resemble a sort of soft, conical, and elongated worms, furnished with six feet, and a large squamous head, more convex underneath than above, armed with strong and hooked mandibles. They respire by the posterio1• extremity of the body, are very vora· cious, and do great injury to fish ponds by devouring the spawn. H. piceus, Fab.; Oliv., Col. III, 39, 1, 2. An inch and a half long; oval; of a blackish-b1·own, polished, or as if covered with a varnish; antenna\ club partly reddish; some slightly marked stJ•ire on the elytra, the posterior extremity of which is rounded laterally, and prolonged into a small tooth at the intemal angle. It swims and flies well, but walks badly. When held loosely in the hand, its sternal spine sometimes inflicts a wound. The anus of the female is provided with two fu~i, by means of which she constructs an ovoid cocoon, surmounted with a point, resembling an arcuated brown horn. Its external tissue is a gummy paste, which, though fluid at first, subsequently hardens, and becomes impervious to water. The ova it contains are arranged symmetrically, and kept in situ by a sort of white clown. These cocoons float on the water. The larva is depressed, blackish and rugose, and has the faculty of throwing back its brown, smooth, round head. This enables it to capture the little Moiiusca which navigate the surface of the water, its back serving as a point d'appui or anvil on which it mashes the shell in order to devour the ani· mal it contains. The body of these larvre becomes flabby as soon as they are caught. They swim with great facility, and are pro· vided with two fleshy appendages beneath the anus which serve to maintain them on the surface of the water, head downwards, when they come there to respire. According toM. Miger,to whom we are indebted for these observations-Ann. du Mus. d'Hist. Nat. XIV, 441-the larvre of other Hydrophilii are de· privcd of these appendages, and neither swim nor suspend ( 1) Zool. Miscel., 111, p. 94. COLEOPTERA. 397 themselves like those of which we liave been speaking. The females of these species swim with difficulty, and carry their ova under the abdom.en enclosed in a silken web; but these species belong to the last subgenera of this tribe. The J(yd,·ophilus proper of Leach consists of species in which the tarsi are identical in both sexes, and not' dilated, the pectoral spine terminates with the poststernum, and in which the scutel is proportionally smaller( 1 ). In all the following Hydrophilii, the two intermediate joints of the antenna! club are exactly transversal, of a regular form, not prolonged into a tooth at either extremity, and without any space between them; the last is obtuse or rounded at the end. The pectus exhibits neither carina nor spine. The tarsi are less, or not at all fitted for natation, but slightly or not ciliated, and terminated by large, equal, and simple hooks. Those in which the maxillary palpi are hardly longer than the antenore, with the last joint shorter than the preceding one, and cylindrical, in which the body is low, and the elytra are truncated at the extremity, or very obtuse, form the genus LIMNEmus, Leach(2). Those, in which the maxillary palpi are hardly longer than the antennre, with the last joint as long as the preceding one or longer, and almost oval, and in which the body is convex, are comprised by the same English savant in two genera. In one of them, the · H YDROBius, Leach, The eyes are depressed or but slightly convex; the anterior extremity of the head is not abruptly narrowed, and the base of the thorax is as wide as that of the elytra(3). In BERosus, Leach, On the contrary, the eyes are very prominent, the anterior extremity of the head is narrowed abruptly, and the base of the thorax is narrower than that of the elytra. The body is very convex( 4). (1) To the HYDRous, Leach, besides the piceus, refer the following species of Fabricius: theater, olivaceus, rufipes, &c. Those, which the latter calls caraboidu, tllipti.cua, &c., are Hydrophili properly so called of Leach. (2) H. griseus, truncatellua, Fab. (3) The Hydrobii scarabreoidea, melanocephalm, orbicularis, &c. (4.) H. luridus, Fab. • |
