The invention provides nucleic acids, and variants and fragments thereof, obtained from strains of Bacillus thuringiensis encoding .delta.-endotoxins having pesticidal activity against pests of the order Coleoptera. The invention further provides mutagenized nucleic acids that have been modified to encode endotoxins having improved pesticidal activity and/or altered pest specificity. Particular embodiments of the invention provide isolated nucleic acids encoding pesticidal proteins, expression cassettes comprising such nucleic acids, and transformed plants and seeds comprising a nucleic acid of the invention. These compositions find use in methods for controlling pests, especially plant pests.