Has genetically modified Bt corn had a negative impact on Monarch butterflies?

"There is no significant risk to monarch butterflies from environmental exposure to Bt corn, according to research conducted by a group of scientists coordinated by the Agricultural Research Service (ARS), U.S. Department of Agriculture. This research was published in the Proceedings of the National Academy of Sciences (PNAS)."  Link References: Proceedings of the National Academy of Sciences:   Monarch larvae sensitivity to Bacillus thuringiensis-purified proteins and pollen. Richard L. Hellmich, Corn Insects and Crop Genetics Unit, Agricultural Research Service-U.S. Department of Agriculture, Ames, Iowa; (515) 294-9343, fax (515) 294-2268, e-mail rlhellmi@iastate.edu. http://www.pnas.org/cgi/content/full/211297698v1 Impact of Bt corn pollen on monarch butterfly populations: A risk assessment. Mark K. Sears, Department of Environmental Biology, University of Guelph, Ontario, Canada; (519) 824-4120 ext. 3921, fax (519) 837-0442, e-mail msears@evb.uoguelph.ca. http://www.pnas.org/cgi/content/full/211329998v1 Corn pollen deposition on milkweeds in and near cornfields. John M. Pleasants, Department of Zoology and Genetics, Iowa State University, Ames; (515) 294-7204, fax (515) 294-8457, e-mail jpleasan@iastate.edu. http://www.pnas.org/cgi/content/full/211287498v1 Assessing the impact of Cry1Ab-expressing corn pollen on monarch butterfly larvae in field studies. Diane E. Stanley-Horn, Department of Environmental Biology, University of Guelph, Ontario, Canada; (519) 824-4120 ext. 4847, fax (519) 837-0442, e-mail destanle@uoguelph.ca. http://www.pnas.org/cgi/content/full/211277798v1 Temporal and spatial overlap between monarch larvae and corn pollen. Karen S. Oberhauser; Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota (612) 624-8706, fax (612) 624-6777, e-mail oberh001@tc.umn.edu. http://www.pnas.org/cgi/content/full/211234298v1 Effects of exposure to event 176 Bacillus thuringiensis corn pollen on monarch and black swallowtail caterpillars under field conditions. M. R. Berenbaum, Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, Illionois; (217) 333-7784, fax (217) 244-3499, e-mail maybe@uiuc.edu. http://www.pnas.org/cgi/content/full/171315698v1