[Specificity and active principle of Bacillus thuringiensis var. israelensis].

Bio-assays of B. thuringiensis var. israelensis on larvae of Drosophila melanogaster, Musca domestica, Culicoides sp. and Chironomus plumosus are negative except in the last case, but only with doses much higher than those which are lethal for mosquito larvae. Tests on mollusks (Biomphalaria glabrata) and golden fishes are also negative. The specificity of action of the H 14 serotype, limited to a few Diptera families, should be mainly related to the special characteristics of its crystals, which are proved to be the only active material by studying the larvicidal power of isolated crystals and of spore-free or crystal-free mutants. The amino-acid composition is one of these characteristics, being similar qualitatively but different quantitatively, when compared with the composition of the other studied H serotypes.