170 INSECTA. 
two stout ganglions, one on the esophagus and the other in the pectus, 
between the first and seeund pair of legs, which give off two remark- 
able 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.; Rees., Insect. Ib., xxii. About eight lines in 
length; cinereous; back of the abdomen red; tail rather shorter 
than the body *. 
Ranatra, Fab. 
The Ranatre only differ from the Nepz in the linear form of their 
body, in their rostrum, which is directed forwards, and in their an- 
terior legs, of which the coxe and thighs are elongated and slender. 
R. linearis; Nepa linearis, L.; Rees., Ib., XXIII. An inch 
long; pale-cinereous, somewhat yellowish; tail as long as the 
body. 
The tuft on its eggs cunsists of but two sete f. 
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 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.—Sieara, Fab. 
Where the scutellum is wanting {; the rostrum is very short, tri- 
angular, and transversely striated; the elytra are horizontal ; the an- 
terior legs are very short, and their tarsi formed of a single compressed 
and ciliated joint; the other legs are elongated, and the two inter- 
mediate ones are terminated by two very long hooks. 
C. striata; Notonecta striata, L.; Rees., Ib., 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 §. 
* Add N. fusca, grossa, rubra, nigra, maculata, Fab. 
+ For the remaining species see Fab., Syst. Ryng. 
* The Notonecta minutissima, Fab., is the type of the genus Sigara of Leach—Lin. 
Prane. ., XIJ. -The anterior tarsi, as in Corixa, consist of one joint, but this Insect 
is furnished with ascutellum. Its thorax is transversal, and body oval, and not linear 
or cylindrical. 
§ For the other species see Fab., Syst. Ryng. 
