"Favorable weather conditions at breeding grounds for monarch butterflies in Mexico are expected to help raise their numbers to possibly more than 100 million this year, about triple of a few years ago, a study released on Thursday said.

But the overall number of the majestic orange and black butterflies that travel thousands of miles (km) on a migration into the United States and Canada is still well below the 1 billion range of two decades ago, the study from a Texas A&M University researcher said.

"It seems conditions have been successful for monarchs overwintering – not too wet or cold, which can be a lethal combination for them," said Craig Wilson, a senior research associate at the university in the Center for Mathematics and Education."

Jon Herskovitz reports for Reuters February 18, 2016. [2]