Studies on the structure of the integument of the silkworm, with special reference to its cuticular lipids

(IX) Lipides of living and shed cuticles of ligatured premature larvae

Abstract

In order to inquire into the problem what changes will take place in the properties and amounts of cuticular lipides of silkworm under the influences of the actions of the metamorphosis hormones and the starvation, the caterpillars were ligaturel in the boundary of head and thorax on the third day of the 4th instar and developed into premature stage. The results of examination of lipides contained in their living and shed cuticles were as follows.
1. In the normal larvae (not ligated) absolute amounts of the total cuticular lipids as well as the ratio of the insoluble parts increase enormously just before pupation ecdysis.In exuviae the lipids are almost entirely composed of the wax-like substances.
2. The ether soluble components contained in the cuticles do not show any increase by the collapse of time in the ligatured premature and normal unfed larvae as compared with the amounts at the time of ligation.
3. The chloroform soluble fractions, on the other hand, show some increases.
4. There are no changes in the amounts of cuticular waxes by ligation and starvation.
5. The lipids are surely larger in content in the exuviae of the ligated larvae from their pupation moult than those from the growth moult, when the comparison are made simultaneously.
6. Thus there are found no changes in the properties and amounts of waxes contained in the cuticles of the ligated premature larvae by the actions of metamorphosis hormones and starvation, but there is an evident increase in the exuviae of pupation moult as compared with those of larval moult (4th moult) with which the hormones have nothing to do.