Environmentalists and beekeepers are calling on the government to ban some of the country's most widely used insect-killing chemicals.
The pesticides, called neonicotinoids, became popular among farmers during the 1990s. They're used to coat the seeds of many agricultural crops, including the biggest crop of all: corn. Neonics, as they're called, protect those crops from insect pests.
Monarch butterflies that once covered 50 square acres of forest during their summer layover in central Mexico now occupy fewer than 3 acres, according to the latest census.
The numbers of the orange-and-black butterflies have crashed in the two decades since scientists began making a rough count of them, according to Mexico's National Commission of Natural Protected Areas.
At a news conference Wednesday, the commission said the count was down 59 percent from December 2011 levels, when the insects filled 7.14 acres of fir trees in central Mexico.