Bacillus thuringiensis Berliner is an aerobic, gram-positive, spore forming, rod-shaped bacterium. It was originally described in 1915 from a diseased Mediterranean flour moth, Anagasta (=Ephestia) kuhniella (Zeller) (Steinhaus, 1949) and has since been found to be pathogenic to a large number of insects, especially the larvae of Lepidoptera. The possibility of using it as a microbial insecticide was first explored extensively in the 1920's and 1930's (Husz, 1928, 1929, 1930, 1931; Metalnikov and Chorine, 1929a, 1929b) (Originals not seen). In 1951, Steinhaus considered the potential of B. thuringiesis in the control of the alfalfa caterpillar. Since that time, research has been done to determine which agricultural pests are susceptible to this bacterium. The success of B. thuringiensis against lepidopterous pesst has led to its commercial mass production and it is currently the only microbial insecticide registered with the United States Department of Agriculture for use on food crops.