Changes in the Distribution of Nitrogen in the Japanese Beetle (Popillia japonica Newman) during Metamorphosis

Abstract

In the absence of histological data an attempt was made to trace by methods of chemical analysis the processes of histolysis and histogenesis during metamorphosis of the Japanese beetle. Analyses of individual insects at all metamorphic stages yielded data for (1) insoluble protein and chitin N, (2) amino-acid N, (3) soluble protein, proteose and peptone N, and (4) uric acid N. These values were expressed in per cent of total N at each stage and their fluctuations charted. A conspicuous change occurs at pupation: Fraction (1) decreases, amino-acid N and Fraction (3) suddenly increases. Changes in the reverse direction have occurred by the 3d pupal day, and the late-prepupal levels are then gradually reconstituted. Uric acid N reaches its peak by the 3d pupal day and apparently shows no further changes. No differences were found between late pupae and adults. It is assumed that decrease in insoluble N and increase in soluble N compounds indicate histolysis, reverse changes indicating histogenesis. The reciprocal shifts in these fractions at pupation do not accompany, but follow, the fall in O2 consumption and in blood pH found by Ludwig (1931, 1934). These latter changes may be considered as manifestations of processes occurring prior to disintegration of larval tissues at pupation.