Effect of ingestion of B. thuringiensis (DiPel 50 IU) on larval hemocytes. Third-instar gypsy moth larvae were fed either distilled water or 50 IU of DiPel (n = 50). Hemolymph was sampled from a separate cohort of five larvae of each treatment at 0, 14, 24, and 32 h post-infection and examined by light microscopy (40×). Representative images are shown, including magnification of individual hemocytes (inset). No differences were observed among larvae from different treatments at 0 h (Additional file 1). Hemocytes from control larvae are adherent and emit pseudopodia (left panel). In contrast, hemocytes from larvae that ingested B. thuringiensis are non-adherent and contain inclusions (center panel). At the time points sampled, the majority of larvae fed B. thuringiensis were still alive. When present, dead larvae that had been fed B. thuringiensis were also sampled (right panel). In dead larvae, only a few abnormal hemocytes were detected and B. thuringiensis cells were present (right panel, insets). No mortality was observed in the controls that were not fed B. thuringiensis. Mortality values of control and B. thuringiensis-treated larvae corresponding to each time point are shown in Table 1.