Two new Bacillus thuringiensis strains, which are deposited at the DSM under accession nos. 5131 and 5132, produce crystal proteins during sporulation that are toxic to Coleoptera. The crystal proteins contain 74 kDa and 129 kDa protoxins, respectively, which can yield 68 and 66 kDa toxins, respectively, as trypsin-digestion products. A plant, the genome of which is transformed with a DNA sequence that comes from either one of the strains and that codes for its respective toxin, is resistant to Coleoptera. Each strain, itself, or its crystals, crystal proteins, protoxin or toxin can be used as the active ingredient in an insecticidal composition for combatting Coleoptera.