Bacillus thuringiensis (Bt) is a microbial biocontrol agent that can be introduced to control butterfly caterpillars. The dried spores of the bacteria is available as sachets and are further mixed with water and sprayed on the plants and trees. The insects when infects the plants and feeds on the leaves will come across the toxin of the bacteria and gets killed. In the gut of the larvae, the toxin is released and the active form of the toxin kills the larvae.