l62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



longest muscles of the proboscis. They originate from the dorsolateral 

 regions of the occiput and are inserted into the sesamoid sclerite, the 

 ventral surface of the hypoglossa near the proximal ends of the para- 

 physes, and the distal extremity of the mentum. By their contraction 

 the entire proboscis is retracted. They are innervated at several points 

 along their length by fibers from the lateral branches of the labial 

 nerve. 



Accessory retractors of the rostrum (fig. 2, AcRtRst). — The origins 

 of these muscles and the next are the sides of the occipital forainen. 

 They are inserted into the ventral integument of the rostrum close 

 to the head capsule. Their contraction assists in the retraction of the 

 entire proboscis. They are innervated by small fibers from both 

 branches of the labial nerve. 



Flexors of the haustellum (figs. 2, 3, FlxHst). — These slender 

 muscles, the second longest in the proboscis, originate at the sides of 

 the occipital foramen laterad of the accessory retractors of the rostrum 

 and pass behind these, whence they extend to flexures of the apodemes 

 of the labrum. By their contraction they flex the haustellum on the 

 anterior face of the rostrum. They are innervated principally by fibers 

 from the lateral branches of the labial nerve. 



Retractors of the oesophagus (figs. 3, 6, RtOcs). — Graham-Smith 

 and Lowne described "small bundles of muscle fibers which arise from 

 the lower part of the frontal sac, or remains of the ptilinum, and 

 which are inserted into the muscular coat of the oesophagus between 

 the fulcrum and the brain. . . . They serve to draw the loop of the 

 oesophagus, which lies between the cephalic ganglia and the fulcrum, 

 forward, when the proboscis is retracted into the head capsule." If 

 these muscles occur in Phormia, they are most inconspicuous. The 

 loop of the oesophagus, as well as the loops of the frontal connectives 

 and the frontal ganglion, are suspended by a network of fine tracheae 

 and fat body extending to the region of the frons and ptilinum. 



There is, however, on each side a fine but conspicuous muscle con- 

 sisting of two strands of fibers, which originates in the integument 

 between the antennal sockets, extends posteriorly, and in the company 

 of the oesophagus and the recurrent nerve passes through the opening 

 which separates the brain and the suboesophageal ganglion. The fibers 

 are inserted into the muscular coat of the wall of the oesophagus 

 posterior to the brain. It is possible that these delicate muscles may be 

 the retractors of the oesophagus ; however, since they apparently pull 

 the oesophagus forward they may more aptly be termed protractors. 



