A theory of tracheal respiration in insects

Abstract

The theory is based mainly on experiments with the larva of the mosquito Aedes (Stegomyia) argenteus. During rest the terminal portions of the tracheoles are filled with liquid. During asphyxiation this liquid is absorbed and the column of air extends towards the tissues, especially the actively contracting muscles. On readmission of air the liquid slowly rises to its original level. During asphyxiation there is an excess of lactic acid in the tissue fluids. Hypertonic solutions of NaCl and K lactate, or the tissue fluids from an asphyxiated larva, introduced into the living larva, also cause extension of air down the tracheoles. Hypotonic fluids cause a slight rise of liquid in the tracheoles. It is suggested that osmotic pressure normally keeps the tracheae of insects more or less full of air, and that the increased osmotic pressure during activity provides for local adjustments in the O supply. Some observations are recorded on the effects of certain poisonous gases and of oil on the tracheal system.