The characteristics of seven crystal-forming Bacillus spp. are compared and an identification key is presented. It is concluded that the following changes in nomenclature are desirable: Bacillus thuringiensis Berliner becomes the type species Bacillus thuringiensis var. thuringiensis n. comb.; Bacillus sotto Ishiwata becomes Bacillus thuringiensis var. sotto n. comb.; and Bacillus cereus var. alesti Toumanoff and Vago becomes Bacillus thuringiensis var. alesti.Two new species, Bacillus entomocidus n. sp. and Bacillus finitimus n. sp., and a new variety, Bacillus entomocidus var. subtoxicus n. sp., are described.

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Regional pH measurements in the gut and the blood of 11 species of Hymenoptera and two of Lepidoptera were made. The larvae were examined in their later instars, after ecdysis, after starvation, or as mature larvae. The gut p H was found to change regionally during development and under these different conditions, but the blood pH tended t o remain relatively unchanged. The pH in the gut and of the blood of the larch sawfly was found t o be close t o the optimum for good growth of B . cereus and mas within the optimum activity range of the enzyme lecithinase in the anterior two thirds of the mid-gut and in the blood. This apparently holds for most of the sawfly species examined and for Carpocapsa pomonella, but not for those Lepidoptera examined herein.

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