276 , THE CANADIAN ENTOMOLOGIST 



The optic, antennal, and fronto-labral nerves arise close together on each 

 side from the cephalo-lateral extension in front of the commissures. 



The Optic Nerve, Opt., Fig. 8, is closely connected with the other two at 

 the base and often with the antennal for a considerable distance. It runs 

 cephalad and laterad, curving behind the dorsal condyle of the mandible and 

 ends abruptly on the hypoderm below the cluster of eyes. From its extremity 

 on or in the hypoderm fine branches proceed to the individual eyes. The 

 Optic is usually closely connected for a portion of its length with the cephalic 

 nerve of the lateral sympathetic. 



The Antennal Nerve, Ant., Fig. 87 frequently appears firmly united at its 

 base with the fronto-labral, giving the latter the appearance of a three-branched 

 nerve; in other specimens it can be distinctly traced backward to the ganglion. 

 It extends cephalad and lateral with the optic, curves sharply caudad and 

 ventrad behind the dorsal condyle of the mandible and enters the base of the 

 antenna, giving nerve-threads to the nerve-like antennal muscles on its way 

 as well as to neighbouring setae. It sometimes lies immediately behind the optic 

 for a considerable part of its length, crossing below the latter beyond the mandi- 

 bular condyle on its way to the antenna. 



The Fronto-labral Nerve, Fig. 8, arises, as already stated, in close conjunction 

 with the antennal and optic. It proceeds directly cephalad along the side 

 of the oesophagus, or pharynx, and presently divides into two main branches. 

 The mesal division, or sympathetic branch, curves regularly to the frontal 

 ganglion upon the meson, and may be considered a part of the sympathetic. 

 It has no branches. The lateral division, or the labral nerve proper, extends 

 directly cephalad to innervate muscles of the pharynx and labrum, and to give 

 certain fibres to the sympathetic. Slightly cephalad of the frontal ganglion 

 it becomes considerably widened and gives off several branches. One passes 

 dorso-mesad to retractor muscles of the pharynx; a slender unbranched strand, 

 "S.br.2", connects the labral nerve with the cephalic ganglion, "c.ge.", of the 

 median nerve; a stouter mesal branch, "m.br.", runs cephalad along the side 

 of the pharynx and enters the labrum; a fourth branch, "ph.br.". passes to the . 

 lower part of the side of pharynx and immediately di\'ides into three main branch- 

 es which innervate that region. The mesal branch of these is directly connected 

 with a ganglion of a sympathetic plexus, "s. gl.," lying upon the hypoderm of the 

 wall of the mouth, and is through the branches of this plexus connected with 

 the cephalic branches of the median nerve. The main division of the labral 

 nerve, L., innervates the labral muscles, as indicated- on the figure^. The outer- 

 most branch runs cephalo-laterad in conjunction with tlie mandibular nerve of 

 that side, but curves sharply mesad at its tip, giving numerous strands t(^ the 

 lateral muscles of the labrum. The details of its branching are shown on the 

 figures. The two connections with the sympathetic vary considerably in differ- 

 ent individuals. In one specimen these two sympathetic connections seemed 

 to be united, one strand from the labral nerve uniting with the plexus, which 

 in turn was connected with the cephalic ganglion. 



The optic, antennal and fronto-labral nerves are varia]:)ly fused at the base; 

 in some individuals the three are united for a third their length, so that one 

 enormous nerve leaves the brain on each side. 



