STUDIES ON THE HEXAPOD NERVOUS SYSTEM. VI. VENTRAL NERVE CORD SHORTENING; A METAMORPHIC PROCESS IN GALLERIA MELLONELLA (L.) (LEPIDOPTERA, PYRALLIDAE)

Abstract

This was traced by measurements made on more than 200 timed vivisections. All segments do not shorten to the same degree. Variations range from no statistically significant shortening, to partial shortening, to shortening with establishment of contiguity between ganglia, to complete shortening with coalescence of ganglia. Under the experimental conditions employed shortening commences about 24 hrs prior to ecdysis, and is completed 30-50 hrs alter. Rates at which 3 of these segments shorten were approximated as 0.27 mm, 0.46 mm, and 0.41 mm/day. The slopes differ significantly from one another. Much of the shortening which occurs is compensated by subsequent elongation of certain connectives. The fact that shortening and elongation are not in phase should facilitate study of the 2 processes. The overall result is an adult ventral nerve cord about 15-20% shorter than that of the larva from which it has developed.