MUSCLES AXD I'lSCERA OF THE IMAGO. 



221 



The muscles of the posterior wing-root consist of six fasciculi ; 

 which arise from the mesothoracic epimeron and the great ento- 

 pleuron. They converge and form two tendons, which are inserted 

 into the sclerites of the posterior wing-roots ; but the exact 

 points of insertion are difficult to determine, as their tendons 

 branch again, and appear to form a plexus with each other. A 

 large branch is inserted into the unguiculus. I have also traced 

 branches of these tendons into various parts of the posterior 

 wing-root. 



I 



m, 



FIG. 3 . /, A transverse section through the mesothorax ; 2, a portion of the same, 

 in a more anterior region, to show the contents of the central blood-sinus : 

 ch, chyle stomach ; / />, fat body ; mm, the dorsales muscles ; m 1 , sterno-dorsal 

 muscle ; r m", leg muscles ; a-, oesophagus ; it, nerve-roots ; s g, salivary gland ; 

 s s, blood sinus ; th g, thoracic ganglion ; tr, paragastric trachea ; /; J , descending 

 trachea ; ti~, ascending lateral trachea ; /;-"', sternal air-sac. 



The gracilis is a curious little muscle with a very long tendon. 

 It arises from the apex of the long process of the parapteron, 

 and is inserted into the parascutal plate. 



4. The Muscles of the Legs scarcely differ from those of Melo- 

 lontha. The flexor, extensor and abductor of the coxa of the 

 anterior leg, as Hammond observed, arise from the paratreme 

 and epitrochlea. These correspond with the three flexors of 

 Straus Durckheim ; there is an adductor which arises from the 



