Bacillus thuringiensis is accepted by most authorities as the valid specific name for insect pathogens in the genus Bacillus with subterminal spores, accompanied by crystals of delta endotoxin, and with biochemical reactions identical to those Bacillus cereus. The main subdivisions of B. thuringiensis, termed 'varieties,' are based on numbered H-(= flagellar) antigens. Within some varieties crystal antigens are used to create subgroups of a lower order ('crystal-types'). Within both varieties and crystal-types, pathogenicity patterns in available host species can be used to characterize categories of a further lower order, possibly best regarded as "strains". Within varieties, uncharacterized isolates should be recorded by accession numbers. No abbreviations of names have been standardized or adopted as trade names and, when first used in a scientific paper, each abbreviation should be defined by the full scientific names.