Back at the lab, they stained and counted the pollen grains to determine how much toxin the caterpillars in each row of experimental plants were likely to have in their diet. That's an important consideration, Cornell's Rayor said. Researchers had criticized Rayor and her co-author, John Losey, for their laboratory experiment, contending that wild caterpillars would never be exposed to fatal levels of the Bt toxin. Rayor acknowledges that the team could have fed the caterpillars a more realistic dose of pollen, but she points out that the caterpillars ate an equal amount of non-Bt pollen. We weren't forcing their mouths open and pouring pollen in.
Timing is another issue.
In the real world, butterflies and corn are not necessarily synchronized, said John Foster, an entomologist at the University of Nebraska-Lincoln. Foster conducted a study last year to find out whether monarch caterpillars are crawling around Nebraska milkweeds at the time the corn is pollinating. He found that 95 percent of pollination was done before the monarch eggs began to hatch. That incredible sense of timing could mean that Nebraska's monarchs are missing the pollen and are safe from the effects of Bt toxin. Foster acknowledges that the situation may be different in other parts of the Corn Belt.