The monarch butterflies are coming, which meant it was time for a party in Coahuila.

The border city of Ciudad Acuña was the site of the annual festival this week to herald the arrival of the migratory insect.

For the last 20 years students of all ages have celebrated the southbound migration with poetry, songs and dance, according to state Environment Secretary Eglantina Canales Gutiérrez, whose department collaborates with the Education Secretariat to organize the event.

“It is a great migration . . . it’s so pretty and interesting that the people and the teachers of the region have taken this migratory phenomenon as symbolic,” she said.

Such festivals highlight the importance of the monarchs in the state and the rest of the country.

Canales told the newspaper Milenio that the first monarchs have already been sighted in the state, and will soon start arriving in the thousands due to the imminent arrival of a cold front.

They always arrive in Coahuila between October 15 and 20, she said.

The number of monarch butterflies arriving to spend the winter in the forests of Michoacán and México state has shrunk by almost 90% in the last 25 years.

The trend reversed during the 2015-2016 season when the area of forest covered by the monarchs jumped from 1.13 to 4.01 hectares, making it the first rise in five years.

But the 2016-2017 season saw another decline, to 2.91 hectares, followed by a similar shrinkage to 2.48 hectares during the last season.

Factors affecting butterfly populations are a decline of milkweed plants for monarchs to lay their eggs on and for the caterpillars to eat, pesticides and insufficient habitat for their journeys north and south, shifting weather patterns and the reduction of forest habitat in Mexico.

Source: Milenio (sp)