The Bt toxin is widely used in agriculture both as a spray and in transgenic plants, yet its precise mode of action against lepidopterans is poorly understood. The study by Mason et al. [mBio 2(3):e00065-11, 2011] revealed that Bt toxin enables an inhabitant of the midgut, Enterococcus faecalis, to enter the hemolymph of larvae and cause septicemia, leading to death.