The popularity of Galleria mellonella larvae as a model to study microbial virulence is due to the similarities that exist between the mammalian and insect immune responses, adherence to the 3R policy and the financial and legal/ ethical burden associated with using vertebrate animal models. G. mellonella larvae have been widely used to assess the virulence of a range of microbial species and the results obtained using larvae closely match those obtained in murine studies. The aim of this project was to utilise G. mellonella to assess the pathogenicity of various human pathogens and compare these results to pathologies that occur in mammals. G. mellonella larvae were infected with Candida albicans, Aspergillus fumigatus, Madurella mycetomatis or Staphylococcus aureus, or co-infected with C. albicans and S. aureus and the host – pathogen interactome characterised by a variety of cellular and proteomic techniques. Infection of larvae with C. albicans and A. fumigatus produced disseminated disease and a similar immune response to the human condition. Infection with S. aureus produced nodules which are similar to abscesses; a hallmark of soft tissue infection in humans. Proteomic profiling of M. mycetomatis grains produced within larvae revealed a range of novel processes (e.g. extracellular vesicle formation, host extracellular matrix binding and response to stress/ host) which are essential in the production of grains in vivo. Co-infection of larvae by C. albicans and S. aureus was characterised, and larvae proved to be an excellent alternative model to study trans-kingdom polymicrobial infection. Larvae were immunological primed by fungal and bacterial cells, and by temperature (37 oC) and their 1) resistance to infection, 2) fluctuations in hemocyte density and 3) alterations in humoral immune response were examined. The effect of two antimicrobial effectors (LL-37 and N-chlorotaurine) of the innate immune response on A. fumigatus were assessed. Exposure to the AMP LL-37 increased the growth of A. fumigatus, the levels of extracellular gliotoxin production, the abundance of proteins associated with growth, virulence and allergenic responses, and increased mortality in G. mellonella larvae. The neutrophil derived oxidant Nchlorotaurine reduced the growth and viability of A. fumigatus, decreased the production of gliotoxin and induced an oxidative stress response. This study demonstrated that larvae are an excellent, cost effective and easy to use model to study host – pathogen interactions, microbial pathogenesis, polymicrobial infection and combination antimicrobial drug efficacy.