Models systems are an essential part of microbiological research as they provide an opportunity to assess the in vivo activity and toxicity of antimicrobial agents or the role of specific virulence factors in disease development in advance of using more sophisticated in vivo systems. Galleria mellonella larvae are now widely used in research and provide results within 48 hours. The immune system of insects shows many structural and functional similarities to the innate immune response of vertebrates and consequently a strong correlation exists between the results obtained using Galleria larvae and mice. G. mellonella larvae may be used to assesses the in vivo toxicity of agents and also their antimicrobial activity. One of the greatest strengths of this system is that it can be used to characterise in vivo disease development processes which are comparable to those that occur during mammalian infection. During dual infection of larvae, Candida albicans increases the pathogenicity of Staphylococcus aureus and results in increased bacterial proliferation, and significant alterations in the proteome of the larvae. Larvae infected with the fungus Aspergillus fumigatus show dissemination of the pathogen and the development of granulomas at sites distant from the point of infection. Results from these types of studies give an insight into how pathogens develop and disseminate during clinically relevant infection and can highlight potential control strategies.