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Show 34 INSECTA. M. Leon Dufour, in the seventh volume of the Animates Generales des Sciences Physiques, has published some very curious observations on the anatomy of the Ranatra linearis, and of the Nepa cinerea. He has discovered in these Insects a peculiar organ which he considers as a kind of pectoral tt·achea communicating with the ordinary trachere. In the first it forms a pair of beautiful tufts of a nact·e-white, and is composed of numerous ramusculi which are directed round a multiplex axis. It is situated in the midst of the muscular masses of the pectus. The pectot·al trachere of the Nepa cinerea appeared to exhibit the vestiges of a pulmonary organ. They consist of two oblong bodies situated immediately under the region of the scutellum, invested by a fine, smooth, satin-white membrane. They are almost as long as the pectus, and, except at the two ends, free. They are filled with a kind of tow which when examined under the microscope presents a homogeneous tissue formed of vascular arbusculi. The nervous system appeared to him to consist of two stout ganglions, one on the esophagus and the other in the pectus, between the first and second pair of legs, which give off two remarkable cords divided at their extremity into two or three filaments. He could only perceive two biliary vessels. To this excellent Memoir we refer the reader both for these details and those relative to the organs of generation, and to the salivary apparatus discovered by its author in these Insects. N. cinerea, L.; Rres., Insect. lb., xxii. About eight lines in length; cinereous; back of the abdomen red; tail rather shorter than the body( I). RANATRA, Fab. The Ranatrre only differ from the Nepre in the linear form of their body, in their rostrum, which is directed forwards, and in their an· terior legs, of which the coxre and thighs are elongated and slender. R. linearis; Nepa linearis, L.; Rres., lb. XXIII. An inch long; pale-cinereous, somewhat yellowish; tail as long as the body. The tuft on its eggs consists of but two setre(2). The others-Notonectides-have their two anterior legs simply curved underneath, with thighs of an ordinary size, and the tarsi pointed and densely ciliated, or similar to those of the posterior ( 1) Add N. fusca, grossa, ruln·a, nigra, maculata, Fab. (2) For the remaining species, see Fab., Syst. Ryng. HEMlPTEHA. 35 ones. Their body is almost cylindrical or ovoid, and tolerably thick or less depressed than in the preceding Insects. Their posterior legs are densely ciliated, resemble oars, and are terminated by two very small and rather indistinct hooks. They swim or row with great swiftness, and frequently while on their back. They compose the genus NoTONECTA, Lin. Which has been divided in the following manner: CoRIXA, Geoff'.-Sigara, Fab. Where the scutellum is wanting(l ); the rostrum is very short, triangular, and transversely striated; the elytra are horizontal; the anterior legs are very short, and their tarsi formed of a single compressed and ciliated joint; the other legs are elongated, and the two intermediate ones are terminated by two very long hooks. C. atriata; Notonecta striata, L.; Rres., lb., XXIX. The largest specimens are about five lines in length; dark brown above, with numerous yellowish dots or little stripes; head, legs, and all underneath, yellowish(2). N OTONEOTA, Geoff. Fa b. Where the scutellum is very distinct, the rostrum forms an arti· culated and elongated cone, the wings are tectiform, and all the tarsi biarticulated. The four posterior legs are geniculate, and have simple, cylindrical tarsi, terminated by two hooks. N. glauca, L., Rres., lb., XXVII. Six lines in length; yellowish above, with a russet tint on the elytra, the inner margin of which is spotted with blackish; scutellum black. To seize its prey with more facility it swims on its back; it stings severely(3). (1) The Notonecta minutissima, Fab., is the type of the genus Sigara of LeachLin. Trans., XII. The anterior tarsi, as in Corixa, consist of one joint, but this Insect is furnished with a scutellum. Its thorax is transveJ•sal, and body oval, and not linear or cylindrical. (2) For the other species, see Fab., Syst. Ryng. ( 3) Fab., Syst. Ryngot.: Lat., Genet'. Crust. et Insect., III, p. 150. The genus Plea, Leach, which that gentleman establishes on the Notonecta minutiasima of Linnreus, and whioh must not be confounded with the one so styled by Fabricius and other entomologists, differs fl·om Notonecta, inasmuch as the third joint of the |