POLLEN from maize genetically modified to produce the Bt insecticide does not
harm all butterflies. Lab tests last year showed the caterpillars of monarch
butterflies died when they ate leaves dusted with the pollen. But field trials
with an unrelated butterfly have revealed no toxic effects.
Entomologist May Berenbaum and her colleagues at the University of Illinois
in Urbana found that black swallowtail caterpillars feeding less than 1 metre
from a field of Bt maize were just as healthy as those feeding 7 metres away,
despite ingesting up to five times more pollen. The concentration of Bt in the
pollen…
