CHANGES IN THE GROSS MORPHOLOGY OF THE VENTRAL NERVE CORD DURING METAMORPHOSIS OF THE WHITE-PINE WEEVIL PISSODES-STROBI (PECK) (COLEOPTERA, CURCULIONIDAE)

Pissodes strobi larvae, pupae and adults were dissected at 24-hr intervals, and the length of the ganglia and interganglionic connectives was measured. The larval ventral nerve cord consists of the suboesophageal ganglion, 3 thoracic and 8 abdominal ganglia. The adult ventral nerve cord consists of the suboesophageal ganglion, a thoracic ganglionic mass, an abdominal ganglion and a terminal ganglionic mass. The first ganglia to fuse are the 2 most posterior abdominal ganglia. These are the only ganglia to fuse in the larval stage. Next the 3 ganglia preceeding the terminal 2 fuse with them. Once begun, these fusions take only 2-3 days. The formation of the thoracic ganglionic mass takes 14 days. First to fuse are the third thoracic ganglion and the first abdominal ganglion. Next, the second abdominal ganglion fuses with these and finally the second thoracic ganglion. Of the original larval ganglia, only the first thoracic ganglion and the third abdominal ganglion remain independent. © 1979.