io8 Annals Entomological Society of America [Vol.1, 



In the following consideration of the details of the larval 

 nervous system I shall first take up the discussion of the central 

 system, and follow this by a consideration of the so-called sym- 

 pathetic system. ^^ 



THE CENTRAL NERVOUS SYSTEM. 



The Supraoesophageal Ganglia or Brain (Figs. 4 and 

 7, h, h). The so-called brain consists of two, large ovoid ganglia, 

 situated dorsad of the oesophagus in the anterior portion of the 

 head and immediately beneath the roof of the head, being pro- 

 tected only by a thin layer of connective tissue. The two ganglia 

 are connected by a short, thick commissure, which in the draw- 

 ing (Fig. 4) is indicated by the constriction between the two 

 halves. • 



The dorsal portion of the anterior enlarged end of the aorta 

 (Fig. 4, 7, ao) is attached to the caudo-ventral border of the brain. 



In the brain of the Corydalis larva, the neuromeres — proto- 

 cerebrum, deutocerebrum, tritocerebrum — are not so well dif- 

 ferentiated as in the brain of Orthopterous insects studied by 

 Viallanes '87, yet indications of the primitive ganglia constitut- 

 ing the brain are found in the form of basal enlargements of the 

 optic, antennal, and the labral nerves which arise from the corres- 

 ponding proto-, deuto-, and tritocerebrum. In the brain of the 

 adult Corydalis, however, the neuromeres are more prominent 

 than in the larva, the brain having undergone great modification 

 during the pupal stage. 



The optic nerves (Fig. 4 and 7, 0, o). The lateral borders 

 of the brain are pushed out into the optic nerve trunks. A short 

 distance from their origin, each trunk divides into seven slender 

 nerves, each of which supplies an ocellus. As already stated, 

 the seventh ocellus is generally rudimentary. The seventh nerve 

 corresponding to this eye, however, is always present. 



The antennal nerve (Figs. 4, 5, and 7, a.a.) This arises 

 from the side of the brain ventro-cephalad of the optic nerve- 

 trunk. The antennal nerve breaks up into three branches, of 

 which the anterior main branch innervates the antenna. The 

 second branch innervates the muscles of the antenna, situated 

 at the base of the saine. The basal branch, a rather slender 

 nerve, originates near the ganglia and extends dorso-laterad. 



The clypeo-labral nerve (Figs. 4, and 7, cl). This together 

 with the arched nerve {ar), originates as a single nerve trunk 



