HEMIPTERA. 169 



Naucoris, Geoff., Fah. 



The labrum in Naucoris is not cmarginatecl, as is the case in the 

 following genus, but is exposed, large, triangular, and covers the base 

 of the rostrum. The body is almost ovoid and depressed, and the 

 head rounded; the eyes are very fiat. The antennae are simple, and 

 without any projection in the form of a tooth. There is no salient 

 appendage at the j)Osterior extremity of the abdomen. The four last 

 legs are ciliated, and their tarsi consist of two joints, with two hooks 

 at the end of the last. 



N. cimicoides ; Nepa cimicoides, L.; Ross., Insect., Ill, Cim. 

 Aquat., xxxviii. Five or six lines long, and of a greenish brown, 

 lighter on the head and thorax ; margin of tlie abdomen serrated 

 and projecting beyond the elytra*. 



In the three following subgenera, the labrum is sheathed, and the 

 extremity of the abdomen presents two filaments. 



Belostoma, Lat., 



Where all the tarsi are biarticulated, and the antennae are semi- 

 pectinated f. 



Nepa, Lat.. 



Or Nepa proper, where the anterior tarsi have but one joint, and the 

 four posterior ones two, and where the antennae appear forked. The 

 rostrum is curved beneath; the coxae of the two anterior legs are 

 short, and their thighs much wider than their other parts. 



Their body is narrower and more elongated than in the preceding 

 subgenera, and almost elliptical. Their abdomen is terminated by 

 two setfc, which enable tliem to respire in the oozy and aquatic loca- 

 lities at the bottom of which they live. Their eggs resemble the seed 

 of a plant of an oval figure, crowned with a tuft of hairs. 



M. Leon Dufour, in the seventh volume of the Animales Gene- 

 rales des Sciences Physiques, has published some very curious ob- 

 servations 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 trachea communicating with the 

 ordinary tracheae. In the first it forms a pair of beautiful tufts of a _ 

 nacre-white, and is composed of numerous ramusculi, which are di- 

 rected round a multiplex axis. It is situated in the midst of the mus- 

 cular masses of the pectus. The pectoral tracheae of the Nepa cinerea 

 appeared to exhibit the vestiges of a pulmonary organ. They con- 

 sist 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 vas- 

 cular arbusculi. The nervous system appeared to him to consist of 



* Fab., Syst. Ryng.; Lat., Gener. Crust, et Insect., Ill, p. 146. 

 t Lat., lb., p. 144; the Nepa grandis, annuhta, ru^iica, Fab. 

 VOL. IV. 



