With its flamboyant orange-and-black wings and incredible 1,000-mile migratory flights, the monarch butterfly is one of the world's best-known and most beloved insects. And like a miner's canary, it has become a kind of biological early-warning system, succumbing to environmental changes long before humans notice them. Last week the monarch sounded another alert--fanning new fears about bioengineered crops.
In a study published in Nature, Cornell entomologist John Losey and his colleagues reported that pollen from corn made pest-resistant by the addition of bacterial genes could spell trouble for monarchs. In his experiments, Losey scattered pollen from the genetically modified corn onto...