Two kinds of antibacterial activities, lysozyme and cecropin-like proteins, were detected in the haemolymph of larvae and pupae of Galleria mellonella injected with live Enterobacter cloacae strain 12, commonly used as a biotic inducer of an immune response in lepidopterans and other holometabolous insects. The induction of antibacterial activity was constitutively depressed by injection of hydrocortisone at an early stage of immune response, but the mode of action of this immunosuppressive agent on the insect cell-free antibacterial immunity remains unresolved.