The largest roost sighting posted to Journey North as of Aug. 26 - by far - was located in roadside trees in south-central Minnesota that are surrounded by vast fields of genetically modified corn and soybeans: http://www.learner.org/jnorth/sightings ... 1346183174
And here's another video I shot of many monarchs and other butterflies nectaring next to huge monocultures of GMO corn and soybeans in the same general region (Aug. 26, 2012 4 miles north of Fairfax, MN along State Highway 4):
http://www.learner.org/jnorth/sightings ... 1346249793
Specifically, DupontPioneer Optimum AcreMax Xtra Corn with the BT traits against the corn borer moth and corn rootwoom beetle and corn that also has the Roundup Ready trait and corn that is grown from clothiandin insecticide treated seed (clothiandin is a neonicitinoid insecticide)