It's hard to say. Did all those fires in the Southwest kill the Monarchs as they migrated from Mexico or the Gulf states? Was the long cold spell here in Minnesota this spring too much for those who did arrive? Are they being killed off by genetically-modified corn pollen from plants with BT (Bacillus thuringensis) built in to kill corn earworms -- and any other caterpillars it comes in contact with? Is climate change upsetting the migration cycle? Is it a combination of all these things? We do know that their wintering habitat in Mexico is shrinking, due to illegal logging of the areas where they normally go. In addition, there are fewer and fewer places for Monarchs to stop along the way.
(Photo by Kenneth Dwain Harrelson
Courtesy of Wikimedia Commons)