Bacteriolytic activity in the salivary glands of adult Aedes aegypti female mosquitoes starts from a low level upon emergence, increases 6-fold over the first 3 days, then levels off. 2. Mosquitoes start sugar-feeding after 2 days, when lytic activity is one-half of the peak level. 3. Bacteriolytic activity in salivary gland extracts is not influenced by removal of corpora allata.