248 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



outer ends of the sternum are the fossae for the attachment 

 of the limbs. 



c. llemove the first thoracic segment and make sketches 

 of the front and side aspects. 



d. The mesothorax and metathorax are much more com- 

 plicated, and together with the first abdominal segment, 

 are soldered together into a firm-walled box. 



(i.) The flattened ventral surface of this box is made up 

 of three pieces. 



1. The mesosternum, which consists of an anterior 

 median portion (Fig. 132, ') and two nearly rectangular 

 posterior prolongations (a", a"). 



2. The metasternum; a somewhat larger plate, which 

 consists of an anterior square tongue (a'"} which fills the 

 space between the posterior horns of the mesosternum ; 

 and a large pentagonal portion (a iv ), which is so placed 

 thut one of its angles points backward along the median 

 line. 



3. The first abdominal sternum (a v , a vi ) is mortised 

 into the posterior margin of the metasternum in nearly 

 the same way that the latter is joined to the preceding 

 sternum. 



(ii.) In a ventral view of the thorax the lower ends of 

 the episterna (c, c', c") and the fossae for the articulation 

 of the legs are visible at the sides of the sterna. 



1. Parallel with the anterior half of the mesosternum 

 are the lower ends of the mesothoracic episterna (c'). 



2. Parallel with the posterior half of the moso^ternurn 

 are the fossae of the second pair of legs. The inner bor- 

 ders of these fossae are not formed by the mesosternum 

 itself, but by slender horn-like backward prolongations of 

 the lower end of the episternum. 



3. Parallel with the anterior half of the metasternum are 



