Abstract
1. The cuticle of the membranous parts such as arthrodial membrane of body trunk, articular corium of thoracic legs and the membranous ring of abdominal legs of the larvae of the rice stem borer, Chilo suppressalis WALKER, consists of epicuticle and endocuticle, but sclerotized exocuticle is absent.
2. The epicuticles in all membranous parts are different in properties from those in sclerotized regions, namely, the wax layer is believed to have such a property and a thickness as to make the passage of liquids easier and the reactions to prove the presence of lipids and proteins in the outer (paraffin) and inner epicuticle (cuticulin) are both weaker compared with those of sclerotized regions.
3. The rate of entry of insecticides is generally faster through the cuticle of membranous parts than that of sclerotic regions. Topical applications of oil emulsions of BHC and Folidol made on various areas of integument resulted in the development of toxic symptoms of the larvae in the order of the rate of permeation, spiracles=thoracic and abdominal legs≥intersegmental membranes≥caudal legs>body sclerites.
4. Such differential penetrability of insecticides may be due to the differences in the structures and the properties of the cuticle of the body regions as described above.
