Fear in Mexico as twin deaths expose threat to monarch butterfliesand their defenders

The deaths of two butterfly conservationists have drawn focus to a troubling tangle of disputes, resentments and violence

The annual migration of monarch butterflies from the US and Canada is one of the most resplendent sights in the natural world - a rippling orange-and-black wave containing millions of butterflies fluttering instinctively southward to escape the winter cold.

The spectacle when they reach their destination in central Mexico is perhaps even more astonishing. Patches of alpine forest turn from green to orange as the monarchs roost in the fir trees, the sheer weight of butterflies causing branches to sag to the point of snapping. Tens of thousands of the insects bounce haphazardly overhead, searching replenishment from nearby plants.