(1) pathogen immobilization (Fig. 1B) , (2) core immune signaling pathways (Toll, IMD and JAK-STAT) (Fig. 1C) and (3) the RNAi pathway (Fig. 1D ). Because there have been several excellent reviews describing these pathways, we only summarize here their key elements, as depicted in Fig. 1 , and refer the reader to other sources for more in depth descriptions (Agaisse and Perrimon, 2004; Akira et al., 2006; Bhavsar et al., 2007; Brodsky and Medzhitov, 2009; Diacovich and Gorvel, 2010; Dionne and Schneider, 2008; Ferrandon et al., 2007; Folsch et al., 2003; Sansonetti, 2008) .