Pathogens that cause disease in insects, known as entomopathogens, are diverse and widespread in the natural world. Fifty per cent of living organisms are microbial, and insect pathogens are ubiquitous in both above-ground and below-ground ecosystems (Vega et al. 2009). The life-history traits of these tiny organisms defy imagination, and the dramatic way in which they affect their hosts is contrary to their size.