The use of mammals for studying micro bial pathogens or for assessing the efficacy of a variety of pharmaceutical agents has contributed enormously to our knowledge of microbial virulence and in the development of novel therapeutic strategies. However, despite these advances, there is a recognition that the number of mammals used in such tests must be reduced to the minimum and that alternative, but ethically acceptable, systems must be developed. This has led to the adoption of the 3R policy by many government and international funding agencies in an effort to encourage the development of more acceptable but scientifically valid screening systems. A variety of models have been developed as alternative systems in recent years including cell culture, tissue explants and nematodes. Insects such as Drosophilia melanogaster (fruit fly), Galleria mellonella (wax worm), and Bombyx mori (silk worm) have become attractive alternative models for studying host pathogen interactions and for assessing the efficacy of novel antimicrobials. The immune system of insects is very similar structurally and functionally to the innate immune response of mammals hence results obtained using insects can readily be translated to mammals. Insects offer a number of advantages as models including high throughput (24– 48 h), ease of inoculation, a lack of ethical restrictions and most can be cultured easily or purchased relatively inexpensively.