MUSCLES OF PROBOSCIS 



59 



The Retractors of the Fulcrum (r.f.). These muscles are 

 attached to the internal anterior edges of the genae, and are in- 

 serted into the posterior cornu (p.c.) of the fulcrum. Their 

 contraction causes the rotation of the fulcrnm nii the epistome as 

 a hinge in the retraction of the proboscis. 



The Retractors of the Haiistellum {r.h.). These muscles have 

 their origin on the d(H-s(>lateral regi<ms of the occiput. They are 

 long and narrow, and running on each side of the common salivary- 

 duct are inserted into the dorsal margin of the theca. 



-\-trs. 



Fig. 28. Transverse section through the lower portion of the head-capsule, show- 

 ing the muscles and tracheal sacs in this region and the fulcrum in section. 

 (Camera lucida drawing.) 



h.p. Floor of pharynx. r.p. Eoof of pharynx. tr.s. Tracheal sac. Other 



lettering as in fig. 3. 



The Retractors of the Rostrum (r.r.). This pair of muscles 

 has its origin at the sides of the occipital foramen, and is inserted 

 into the posterior side of the membranous rostrum about half way 

 do^vn its length. In the retraction of the proboscis these muscles 

 draw in the rostrum. 



The last two pairs of muscles acting together assist in the 

 retraction of the whole proboscis. 



The Flexors of the Haiistellum {f.h.) have their origin close to 

 that of the retractors of the rostrum at the sides of the occipital 

 foramen. They are inserted into the base of the labral apodeme 



