Insects are the most numerous and diverse group of animals on earth, not only in number of individuals, but also in number of species. They inhabit virtually all terrestrial and freshwater environments, where they must protect themselves from an array of commensal, pathogenic and parasitic organisms that share the same ecological niches. Since the early 20th century, scientists have been intrigued by how insects defend themselves against microbial attack. We are currently witnessing a break-through in our understanding of the mechanisms governing immune reactions in insects. Molecular...