Some Aspects of Segmentation

Abstract

The body of an insect is subdivided into a number of periodic units called segments, morphologically definable in terms of the pattern elements they contain. Segments are built up by derivatives of the mesoderm and ectoderm, e.g. muscles, trachea, nervous system, epidermis, whilst endodermal derivatives are neither segmentally organized nor do they display any obvious metameric distribution. Borders between segments of insects are morphologically defined by intersegmental furrows and by apodemes for insertion of muscles. We want to emphasize that there is no major ambiguity while morphologically defining the pattern elements of a segment and the segmental borders.