Death by natural causes

Reports that pesticides killed 22 million monarch butterflies in Mexico were
greatly exaggerated, say the World Wildlife Fund and US researchers.
Environmentalists told Reuters last week that loggers had sprayed forests in
central Mexico with pesticides so that they could be reopened for logging. But
Monica Missrie of the WWF in Mexico City told New Scientist that the
mass deaths were probably caused by cold. Recent heavy snowfalls would have
killed off a few million butterflies, she says. “It’s been overblown.”