PROBOSCIS OF PHORMIA REGINA — DETHIER 



l6l 



MUSCLES ORIGINATING IN THE HEAD CAPSULE 



Retractors of the fulcrum (figs, i, 3, RtFul). — These are short, 

 robust muscles originating on the internal anterior edges of the genae. 

 They are inserted into the extremities of the posterior cornua of the 



SOE GNG 



Fig. 2. — Muscles and labial innervation of the proboscis of Phormia regina 

 Meigen, anterior aspect. 



O, ocelli; SoeGng, subocsophageal ganglion; RtRst, retractor of rostrum; 

 LbNv, labial nerve; AcRtRst, accessory retractor of rostrum; FlxHst, flexor 

 of haustellum ; MxPlp, maxillary palpus ; AdA, adductors of apodeme ; ExHst, 

 extensors of haustellum; FlxLm, flexor of labrum; Ap, apodeme; DCor, distal 

 cornu of fulcrum. 



fulcrum. As described by Lowne (1892) and Graham-Smith (1930), 

 their contraction causes the lower end of the fulcrum, i.e., the region 

 of the distal cornua, to describe a circular arc so that the fulcrum is 

 retracted to a horizontal position between the genae. These muscles 

 are innervated by fibers from the lateral branches of the labral nerve. 

 Retractors of the rostrum (figs. 2, 3, RtRst). — These are the 



