1920] Dit Porte: Muscular System of Gryllus 25 



(b) Dorsal. 



4. The Elevator of the Head. A strong double interseg- 

 mental muscle. One head originates from the first inter- 

 segmental sclerite (Fig. 1, in.), the other from the posterior 

 edge of the pronotum near the median line. The two are 

 inserted by a common elongated tendon into the lateral apodeme 

 (Fig. 2, AL.) of the dorsal border of the occipital foramen. 

 [139, 140, 1st and 2nd tergal muscles of the veracervix]. 



(c) Pleural. 



5. The Retractor of the Head. Origin, anterior edge of the 

 pro-episternum ; insertion, lateral side base of head. [138, Fifth 

 (a) sternal muscle of the veracervix]. 



PLEURAL MUSCLES. 



(a) Noto-pleural. 



6. The First Rotator of the Head. Origin, anterior edge 

 of the pro-episternum; insertion (1) median apodeme (Fig. 

 1, A. M.) of the dorsal border of the occipital foramen, and (2) 

 anterior edge of the first intertergite. [141, 142, first and 

 second external rotators of the head]. 



7. The Second Rotator of the Head originates from the 

 anterior edge of the pronotum near the median line and is 

 inserted into the postero-dorsal edge of the interpleurite near 

 the dorsal angle. [143, the intersegmental muscle of the 

 veracervix] . 



8. The Third Rotator of the Head, originates from the 

 pronotum just in front of the distal end of the pleuron and is 

 inserted into the ventral edge of the interpleurite. [144, second 

 intersegmental muscle of the veracervix]. 



9. 10. The Fourth and Fifth Rotators of the Head. Both 

 originate from the interpleurite and are inserted into the 

 median apodeme (Fig. 1, A. M.) of the dorsal border of the 

 occipital foramen. [146, 147, second and third dorsoventral 

 muscles of the veracervix]. 



11. The Sixth Rotator of the Head. From the apodeme of 

 the interpleurite to the lateral apodeme of the foraminal border. 

 ■[148, fourth dorsoventral muscle of the veracervix]. 



12. The Seventh Rotator of the Head. Origin, apodeme of 

 interpleurite; insertion, neck membrane behind the first inter- 

 tergite. [145, first dorsoventral muscle of the veracervix]. 



