Following publication yesterday of a study that found genetically modified corn can kill monarch butterflies, the European Union governing body suspended approval for two types of gene-altered corn. Two other types have already been approved by the EU. In all, 18 genetically modified products have been approved by the EU since 1992; however, there has been little or no commercial planting of gene-altered seeds in Europe. Environmentalists in Mexico, where millions of monarchs spend their winters, are calling on the Mexican government to ban the use and importation of genetically modified corn.