The Cuticle of Some Lepidopterous Larvae II

Abstract

In both the larvae of Hemerophila atrilineata BUTLER and Cnidocampa flavescens WALKER, there are changes in histological structure of the cuticle in passing from one sclerite to the next behind. They are clearly shown after staining with HEIDENHAIN'S iron haematoxylin and with MALLORY'S triple stain. In the larva of Hemerophila atrilineata, the sclerites (tergites) are colored by the presence of an exocuticle, the outer layer of which, is yellowish brown or amber. The inner layer resembling the outer in being homogeneous and refracticle, however, is colorless. At the anterior and posterior margins of the sclerite the colored as well as the colorless exocuticles progressively decrease in thickness and disappear as the arthrodial membrane is approached. In the larva of Cnidocampa flavescens, the whole regions of the cuticle are colorless, although the cuticular structure is specialized in the different regions. Four distinct layers are readily recognizable in the sclerites, while only two in the arthrodial membranes. The median two layers in the sclerite may be regarded as parts of the endocuticle, because they are neither haematoxylinophilic nor fuchsinophilic indicating that tanned protein and lipid are not impregnated. At the anterior and posterior margins of the sclerite, the median two endocuticles become thinner and disappear as approaching the arthrodial membrane.
In both the larvae of Barathra brassicae LINNÉ and Euxoa segetis SCHIFFERMÜLLER, the cuticles present an uniform structure over whole regions. They consist of the epicuticle, the exocuticle and the endocuticle.