A bollworm is a common term for any larva of a moth that attacks the fruiting bodies of certain crops, especially cotton. B. thuringiensis (commonly known as Bt ) is an insecticidal bacterium, marketed worldwide for control of many important plant pests - mainly caterpillars of the Lepidoptera (butterflies and moths) but also mosquito larvae. During sporulation, many Bt strains produce crystal proteins (proteinaceous inclusions), called as endotoxins or cry proteins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops using Bt genes.