Large ocellar interneurons in the brain of the cabbage looper mothTrichoplusia ni (Lepidoptera)

Abstract

The topography of ocellar interneurons in the brain of the cabbage looper moth,Trichoplusia ni, was examined with the use of the cobalt infiltration and Timm's silver-sulfide intensification techniques. Two interneuron tracts are found in each half of the brain. One nerve tract is composed of 6–7 first order interneurons whose axons run to the ipsilateral side of the brain and terminate in the ventral protocerebrum. The other nerve tract is composed of 3 interneurons. Two of these are first order interneurons which project to the contralateral side of the brain where they terminate in the posterior protocerebrum. A third interneuron has processes connecting the two lateral ocelli and projects to both the ipsilateral and contralateral protocerebrum. Several small fibers are also present. Some of these extend to the lobula and the optic tubercule. A classification of ocellar interneurons for comparative study is proposed.