Histological and ultrastructural study of the adipose tissue of Aedes aegypti has shown that infection with the filaria Dipetalonema dessetae locally induces a highly active synthesis of proteins (formation of ribosomes, endoplasmic reticulum and Golgi complexes, multiplication of mitochondria). This phenomenon appears similar to the effect of beta-ecdysone after the up-take of blood. Mosquitoes let to starve during the development of the filaria show a quick disappearance of storage substances (lipids and glycogen) and involution forms of the induced ergastoplasma (after seventh days only), so that the infected tissue degenerates and the development of the filaria is arrested.