132 INSECTA. 



species, called Travellers, unite in troops so considerable that, 

 upon rising, they resemble a dark cloud, and convert all 

 places where they sojourn into deserts. Their death is a new 

 scourge ; for, in putrefying, their bodies often emit exhala- 

 tions which produce epidemic diseases. In certain parts of 

 Africa the Insects are collected for eating, and also preserved 

 in brine for commerce. 



ORDER IV. HEMIPTERA. 



Two wings covered by two elytra, generally membranous 

 at their free extremity ; mouth formed by a kind of articu- 

 lated tube, curved inferiorly, resembling a beak, and exhibi- 

 ting a groove including four stiff, pointed hairs, which have 

 been considered as the rudiments of mandibles and jaws, 

 organs which have disappeared in these Insects ; metamor- 

 phosis generally incomplete ; many have smooth eyes, but 

 never more than two. Two sections. 



Section I. Heteroptera. 



Beak springing from the front ; elytron membranous at the 

 extremity; elytra and wings always horizontal, or slightly 

 inclined. 



GENUS I. CIMEX, Lin. 



Three joints to the tarsi ; antennae longer than the head, 

 and inserted between the eyes. 



SDBGENUS PENTATOMA. 



Elytra crossed, and partially coriaceous ; antenna? with five 

 joints. 



SUBGENUS CIMEX PROPER, Lat. Bed-Bug. 



Body wide, entirely without wings, and exceedingly de- 

 pressed ; antennae with four joints, terminating abruptly in 

 the form of setae. 



GENUS II. NEPA, Lin. Water- Scorpions. 



Antennae inserted and concealed under the eyes ; they are 

 shorter than the head, or, at least, of the same length ; ante- 



