Bacillus thuringiensis is a gram-positive, soil-dwelling bacterium, and is the most commonly used biological pesticide worldwide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on leaf surfaces, aquatic environments, animal feces, insect-rich environments, flour mills and grain-storage facilities. It has also been observed to parasitize moths such as Cadra calidella—in laboratory experiments working with C. calidella, many of the moths were diseased due to this parasite.