Pore Canals of the Insect Cuticle

Abstract

IT has been suggested from time to time that the pore canals of the insect cuticle offer an important channel for the entry of contact insecticides, and Wigglesworth¹, working on the bug Rhodnius, in which the canals contain protoplasmic filaments, or perhaps fluid, has recently given additional evidence in favour of this view. But Richards and Anderson², as a result of their electron microscope studies of the cockroach cuticle, believe that the pore canals are filled by a watery fluid and not by protoplasm, and that oil-borne insecticides cannot penetrate by this route. Among earlier writers Holmgren³, Plotnikow⁴, and Berlese⁵ have expressed the view that although the canals are occupied by protoplasm during early growth of the cuticle, they are later filled by some cuticular substance. If this is so, they would appear scarcely likely to be involved in insecticide penetration.