PROBOSCIS OF I'HORMIA REGINA — DETHIER 167 



the antennal nerves. They are smaller in diameter than the antennal 

 nerves. They pass down the proboscis on either side of the oesopha- 

 gus. Each one shortly branches. The branch nearer the midline divides 

 again, and part of it curves anteriorly and dorsally meeting the cor- 

 responding branch of the opposite side and uniting with it in a single 

 nerve. This nerve loops to continue ventrally for a short distance 

 along the oesophagus before looping once again to reverse its direc- 

 tion and continue dorsally and posteriorly up the oesophagus as the 

 recurrent nerve (figs. 3, 4). The recurving branches are the frontal 

 connectives. In some specimens the frontal connectives leave the main 

 trunk before it branches (fig. i). The exact disposition of the loops 

 varies depending on whether the proboscis is retracted or extended ; 

 however, the first recurved dorsal loop is constant even though its 

 tightness varies. It is suspended from the anterior walls of the pro- 

 boscis and the anterodorsal wall of the head capsule in the region of 

 the remnants of the ptilinum by strands of fine tracheae and fat body, 

 both of which by their elasticity permit great flexibility and shock- 

 absorption of the nerves as the mouth parts move. The most ventral 

 extension of the nerve, before it retraces its dorsal course, gives rise 

 to a small nerve which continues for a short distance down the oe- 

 sophagus (fig. 4). It also gives off to the surface of the oesophagus 

 at least two lateral pairs of very fine nerves. 



The exact position of the frontal ganglion is difficult to ascertain 

 because it is not conspicuously ganglionlike in appearance. After 

 the two frontal connectives fuse, there is a swelling in the region of 

 the first loop and another in the region of the second loop. It is prob- 

 able that the first is the frontal ganglion. 



The recurrent nerve continues along the anterior surface of the 

 oesophagus as it traverses the brain (fig. 3), Emerging posteriorly 

 from the brain, it proceeds along the dorsal surface of the oesophagus 

 and joins the hypocerebral ganglion just anterior to the junction of 

 the crop and proventriculus (figs. 4, 6). Here small nerves branch 

 to the corpus allatum and corpus cardiacum. The largest nerves from 

 the hypocerebral ganglion extend to the crop and to the proventriculus. 



After the frontal connectives branch from the labro frontal nerves, 

 the two medial nerves unite on the anterior surface of the oesophagus 

 in the region of the insertions of the retractors of the fulcrum. The 

 fused nerve then extends down the proboscis passing between the 

 paired dilators of the cibarial pump to which small branches are sent. 



The lateral branches of the labro frontal nerves pass ventrally on 

 either side of the oesophagus, each giving a branch to the retractors of 



