thuringiensis strains having the characteristics of nrrl b 18195 nrrl b 18196 and nrrl b 18197 require an aqueous nutrient medium which contains a leucine valine amino acid complex for optimum crystal production of the invention bacteria the specifically preferred media composition is the following 0 3 tryptone 0 2 tryptose 0 45 yeast extract made 0 01m in sodium phosphate buffer at ph 6 8 with the addition of 10 8 m mgso 4 and 10 9 m mnso 4 after autoclaving other appropriate medium having the required amino acid complex may be used for growth of the bacteria of the invention however media used other than the preferred medium may result in a diminished crystal production production of the cells is effected under aerobic conditions at any temperature satisfactory for growth of the organisms of the invention i e from about 10 u00b0 c to 40 u00b0 c the preferred temperature range is about 27 u00b0 c to 32 u00b0 c the ph of the nutrient media suitable for growing the b thuringiensis culture is about neutrality i e ph 6 7 to 7 2 incubation time is that time necessary for complete spore and crystal liberation and is preferably about 18 to 24 hours cells may be grown in any conventional baffled shake.