1 66 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



Transverse muscles of the haustellum (fig. 5, TrHst). — These 

 originate near the midline of the internal surface of the mentum and 

 are inserted on the paraphyses. They assist in extending the oral disc 

 by shortening the paraphyses. They are innervated by branches of 

 the labial nerve. 



Dilators of the lahrum-epipharynx . — These are short muscles origi- 

 nating on the internal surface of the labrum and inserting into the 

 outer surface of the epipharynx. Presumably they cause alteration 



PAR 



RtPar 

 Lbnv 



lm ep 



TrHst 



epFur 



LP FUR 



Fig. 5. — Muscles and innervation of the oral disc of Phonnia rcgina Meigen, 



lateral aspect. 



CcP, cochleariforni process ; CpFur, central process of furca ; EpFur, epifurca ; 

 La, labellum ; LbNv, labial nerve ; LmEp, labrum-epipharynx ; LpFur, lateral 

 process of furca ; Mn, mentum ; A'', nodulus ; Pm', paraphysis ; RtFur, retractor 

 of furca ; RtPar, retractor of paraphysis ; TrHst, transverse muscle of 

 haustellum. 



of the diameter of the epipharyngeal cavity (Graham- Smith). They 

 are innervated by fibers from the labral nerve. 



INNERVATION OF THE PROBOSCIS 



The most conspicuous nerves leading from the brain are the paired 

 antennal nerves, the so-called median ocellar nerve, and the paired 

 labro frontal nerves. The large paired labial nerves connect with the 

 suboesophageal ganglion. The proboscis is innervated entirely by 

 the labro frontal and the labial nerves. 



Lahrofrontal nerves (figs, i, 3 LrFrNv). — The labrofrontal nerves 

 extend from the brain from positions slightly ventrad and mesad of 



