Listeria can infect numerous living animals including most mammals and some insects. Two insect species, Drosophila melanogaster and Galleria mellonella (the wax moth) are useful model systems for studying Listeria. Optimal growth conditions for wax moth are 37 degrees centigrade, the same as human body temperature. Listeria strains behave similarly in wax moths and other animal models. Strains virulent in mice are also virulent in wax moth. Strains non-infective in mice are non-infective in wax moth. Compared to mice, wax moth caterpillars are cheap and easy to rear, they are easy to inject with pathogen and can supply equivalent tissue to mice studies.
Studies on wax moth caterpillars do not raise many of the ethical issues of studies on mammals. Listeria is not the only disease studied in wax moth. Several pathogens of humans and companion animals can also be studied in wax moth caterpillars.