Some studies regarding invertebrate–fungal interactions have used the terms parasite and pathogen interchangeably which adds to the confusion when it comes to definitions (Meyling and Hajek, 2010; Kaya and Vega, 2012). The most widely adopted definitions of these terms in the field of invertebrate pathology within the context of biological control remains those of Onstad et al. (2006). They define a parasite as “an organism that lives at the expense of its host, obtains nutrients from the living substance of the latter, deprives it of useful substance, or exerts other harmful influence upon the host.” In this sense, a parasite weakens the host immune system, making the host more vulnerable to foreign infectious microorganisms (Fig. 5). Therefore, if death of the infected occurs, it does as a direct result of foreign organisms and not of the parasite itself. In epidemiological and ecological studies, the term parasite is usually categorized into two groups: microparasite and macroparasite. The latter one, considered a true parasite, is intensity-dependent meaning that its impact on the host is directly correlated with an increase in the number of infection events (Lafferty et al., 2008; Vega et al., 2012). In contrast, microparasites are analogous to pathogens in that they are intensity-independent—a single infection unit leads to an increase in the number of infectious fungal propagules on the host that further weakens the host or leads to disease (Anderson and May, 1981; Lafferty et al., 2008; Vega et al., 2012).