A new study published online August 19 in Oecologia (http://link.springer.de/link/service/journals/00442/) provides evidence that pollen from Bt transgenic corn kills larvae of the monarch butterfly, Danaus plexippus. This contradicts earlier fieldwork that suggested nontarget lepidopteran larvae were unaffected by Bt corn pollen (Nat. Biotechnol. 18, 701, 2000). The two-year Iowa State (Ames, IA) study compared the effects of two Novartis Seeds (Golden Valley, MN) transgenic corn strains against genetically similar nontransgenic hybrids. When monarchs fed on milkweed (their natural food source) for 48 h within 10 meters of the transgenic cornfield plots, 20±3% mortality was observed, as opposed to no mortality when fed near nontransgenic corn. Pollen densities were measured (1–217 pollen grains/cm2) and mortality was observed on leaves with as few as 10 transgenic pollen grains/cm2. When the experiment was simulated in the laboratory, 135 pollen grains/cm2 resulted in mortality levels similar to field treatments. However, transgenic corn pollen had no effect on surviving butterflies' development time, wing length, or lipid content. The data suggest that Bt corn can affect the survival of nontarget lepidopteran insects up to 10 m from cornfields, although certain experts have reservations about the data (see p. 1031).