26 Annals Entomological Society of America [Vol. XIII, 



(b) Sterno-pleural. 



13. The Cruciate Rotators of the Head, originate from the 

 anterior edge of the procoxae and are inserted into the narrow 

 anterior portion of the interpleurite of the opposite sides. 

 [134, the second sternal muscle of the veracervix]. 



Voss, ('05), regarding the cervical interpleurite as a sternal 

 sclerite, describes 13 as a longitudinal sternal muscle, and 6 

 to 12 as dorsoventral muscles. I have followed Crampton ('17) 

 in regarding the interpleurite as a pleural sclerite, in which case 

 these muscles are sterno-pleural and noto-pleural respectively. 



The several rotators working in pairs function as elevators 

 and depressors. 



III. MUSCLES OF THE THORAX. 

 A. The Prothorax. 



LONGITUDINAL MUSCLES. 



(a) sternal. 



XIII. The First Prosternal Muscle (Fig. 21) is a flat unpaired 

 median muscle which originates in the posterior edge of the 

 median entosternite spira of the prothorax, and is inserted into 

 the anterior edge of the spira of the mesothorax. A retractor 

 of the thorax. [102]. 



14. 14a. The Second Prosternal (Figs. 20 and 21). From 

 the median entosternite, into the anterior side of the base of the 

 coxa. A weak extensor of the coxa. [103]. 



15. The Third Prosternal (Fig. 20). From the prothoracic 

 spira obliquely backwards into the distal section of the meso- 

 furca. [104]. 



16. The Fourth Prosternal (Fig. 20). Origin, base of pro- 

 thoracic furca; insertion, mesothoracic furca near 15. [105]. 



17. The Sixth Prosternal (Fig. 20). Origin, furca near 16; 

 insertion, mesothoracic spira. [107]. 



18. The Seventh Prosternal (Fig. 20). From the spira 

 into the base of the furca. [108]. 



The Longitudinal Prosternal muscles are retractors pulling 

 the prosternite and mesosternite together and bending the head 

 and prothorax downwards. The Longitudinal Pronotals are 

 the antagonist muscles of the prosternals. 



