1 68 THE JNTEGUMENTAL SKELETON OE THE IMAGO. 



Bounding the mesosternum (jo) above and behind is a curved 

 suture, the sterno-pleural ; and extending upwards from the 

 sternopleural suture to the posterior spiracle is the hypo- 

 pleural suture. 



The following plates will be readily distinguished : A large 

 square plate {i8) continuous with the mesosternum in front of 

 the sterno-pleural suture. This I term the lateral plate ; its 

 nature has been much discussed. I believe it is a portion of 

 the great mesosternum, which in the Bees (Bombus) and in 

 many Orthoptera always extends upwards to the dorsum. 

 Brauer incorrectly regards it as the episternum. It is certainly 

 not the episternum of Audouin. In some Lepidoptera and 

 other insects the sterno-pleural suture reaches the spiracle, 

 when the lateral plate becomes a separate sclerite. 



The plastron of the mesosternum ( ,0) is the large plate below 

 the sterno-pleural suture. Behind it are the two sclerites 

 of the coxa of the intermediate leg {p, q) and the lateral part 

 of the metasternum i^j). Above the latter, the posterior 

 spiracle is situated ; and between the hypopleural, sterno- 



Description of Plate VII. 



Fir.. I, The Exterior, and Fig. 2, The Interior of the Thoracic .Skeleton : /, scutellum ; 

 2, scutum ; J, prescutum ; 4, posterior dorso-pleural diarthrosis ; J, great alar 

 apophysis ; 6, scutal pouch ; 7, ridge on alar apophysis ; 8, small tympanic 

 plate ; 9, jDosterior parascutal plate ; 10, apodeme of parascuta ; 11, anterior 

 parascutum ; /2, uncinate process ; ij, head of alar apophysis ; 14. and yj", 

 anterior alar fossa ; 16, great ampulla ; jy, parapteron ; iS, lateral plate ; ig, 

 anterior spiracle ; 20, paratrenie ; 21, tympanic ridge ; 22, lateral plate of post 

 scutellum ; 2j, mirror ; 24, tympanic plate ; 2j, costa ; 26, epimeron ; 2y, ridge 

 between epimeron and episternum ; 2S ; episternum ; 2ip, great entopleuron ; jo, 

 mesoplastron ; j/, hypotreme ; j2, epitrochlea ; jj, prodorsum ; ^4, neck ; jj, 

 process of epitrochlea ; j6, root of the haltere ; jj, ridge aljove the posterior 

 spiracle ; jS, scaphoid process of the mesophragma ; jt?, the mesophragma ; 40, 

 spiracle ; 41, epimeron, and 42, episternum of the metathorax ; 4^, metaplastron ; 

 44, entosternum of metathorax ; 4J, furca of mesosternum ; 46, posterior coxa ; 

 47, intermediate coxa ; 4S, 4g, and 50, articular heads on the meso- and meta- 

 sterna for articulation with the coxa; ; j/, vertical plate of metasternum ; 5^, 

 mesoplastron ; jj, vertical plate of mesosternum ; a, part of the shield of the 

 postscutellum ; b, c, posterior alar apophysis ; d f, supra-tympanic fissure ; ^, 

 ' great alar apophysis ; //, post-alar fossa ; /•, hypopterygium ; /, sacculus ; m, great 

 tympanic membrane ; ;/, tympanic bulla ; 0, halter ; /, posterior, and </, anterior 

 sclerites of the intermediate coxae ; r, posterior, and s, intermediate femora ; t, 

 anterior coxa. 



