•^ INTRODUCTION. 



on the lower surface of the liead, are inserted 2 Antennae of 3, -i, or 

 5 joints. The under side of the head ia the Gttla, the sides, ante- 

 riorly, are the Cheeks {gence). In front of the head beneath is 

 inserted the exterior suctorial mouth called the Sostrum ; it is an 

 extension of the labium, consisting of 3 or 4 joints ; the sides are 

 curved upwards, and are united at the edges to form a sheath ; at 

 the base, on the upper side, the lahrum is more or less produced, and 

 closely appressed. Inside lie the representatives of the mandibles and 

 maxillae, in the form of 4 setse ; the maxillary and labial palpi are 

 obsolete. The junction of the rostrum with the head is more or less 

 flexible, and so permits the extension of the organ when in use, or 

 its retraction under the body when in repose. 



The TJiorax. — Of the three thoracic segments the 1st is the 

 Protliorax, of which the upper side is developed into the large plate 

 adjoining the head, called the Pronotum. The lower side, to which 

 is attached the 1st pair of legs, is the Frosternum. The 2nd 

 segment is the Mesothorax : the upper side is the Mesonotum, de- 

 veloped posteriorly into the triangular plate which lies between the 

 elytra, or sometimes covers them, called the Seidell um ; to the lower 

 side, or Mesosternum, is attached the second pair of legs ; and to the 

 sides are attached the Elijtra. The 3rd segment is the Metathorax ; 

 the upper side or Metanotum is very short ; the lower side {Meta- 

 sternum) is longer, and bears the 3rd pair of legs ; here also, on each 

 side, anteriorly, near the coxa, is the orifice of the internal sac, con- 

 taining the matter which gives to so many of the Hemiptera their 

 disagreeable odour. To the sides of this segment are attached the 

 Wings. The under side of the 3 thoracic segments, taken together, 

 is called the Sternum. The prolongation of the middle of the 

 posterior margin of the segments of tlie sternum is the Xyphus. 



The Elytra or wing-covers {Ilemielytra of authors) are usually of 

 two different textures, the basal part being of a firm or leathery con- 

 sistence, and the apical part delicate and membranous. Each elytron, 

 taken as a whole, has its base, anterior (or outer), inner, and posterior 

 margins, its surface being the disk, and the relative parts of eacli 

 subdivision of the elytron, have the same appellations. The basal 



