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Chester County Press

Habitat of monarch butterflies seriously threatened, expert says

09/28/2021 07:49PM ● By Richard Gaw

By Richard L. Gaw

Staff Writer

At a Sept. 24 presentation at the Kennett Farmers Market that celebrated the pollination and migration of the monarch butterfly, expert Gary Liska told an audience of 50 that the insect’s future is being threatened to the point where its current habitat is as delicate and fragile as one of its beautiful wings.   

Liska, who plants private gardens laden with milkweed in order to attract the insect – was one of two presenters at an event sponsored by Historic Kennett Square, the Mt. Cuba Center, the Kennett Library and Casa Guanajuato Kennett Square, a non-profit organization that encourages and promotes the culture, traditions, arts and education of Mexican community in Chester County.

Liska said that while the monarch butterfly remains “one of the greatest pollinators out there,” its population has reduced by 90 percent over the past 25 years.

While the annual migration of the Eastern monarch butterfly is impressive – it flies as many as 2,500 miles from the U.S. and Canada where they breed, all the way down to the forests in central Mexico where they hibernate – the migration is under threat from several sources.

Liska pointed to one possible factor – the proliferation of the tropical milkweed that primarily grows in the southeastern portion of the U.S. While it has exploded in popularity and proliferation, he said it posts serious threats to the viability and frequency of the monarch’s migrations.

Because of that, “those monarchs never migrate, and if they don’t have that, it throws off their natural migration cycles to Mexico,” Liska said. The warmer we get and the average night time temperatures become, the more it will affect the flora, that have a significant impact on a monarch butterfly’s cycle and what they are programmed to do.”

They key problem for the monarch butterfly with the tropical milkweed plant is that they follow their primary food source, and because it is an all-year plant, it becomes the primary source of sustainability for the insect.

Subsequently, “they will strand the monarchs to the point where they can’t migrate and keep them around longer than what they should have,” Liska said. “The types of milkweed that die off naturally is a program for them to move south, but if you throw in a new food source that doesn’t [die off], that’s a huge problem.”

Man-made decisions are also taking a devastating toll on the monarch butterfly. The continued deforestation of Mexican forests have seen tall grasses filled with milkweed – full of white sap that both sustains and protects the monarch butterfly – being converted into farmland. In addition, the increased usage of herbicides in farming such as glyphosate and dicamba -- meant to kill milkweed -- have also become factors in the insect’s dwindling numbers.

The entire life of a monarch butterfly is not only fragile, it is lucky, as well. In his overview of the monarch butterfly’s pollination and migration efforts, Liska said that of the more than 300 eggs that a female monarch butterfly lays, only a few get to reach butterfly stage. While in caterpillar form, it becomes susceptible to attacks by predators like birds and insects, at the same time it grows to 600 times its size at birth in as little as 14 days.

In order to better track the migration efforts of the monarch butterfly, Liska said that he places between 200 and 300 tracking tags on the forewings of mature butterflies on his property in partnership with Monarch Watch, a national organization that conducts research and preservation efforts for the monarch butterfly.

Each four-letter, three-number tag that Liska applies will enable experts to track a particular monarch to Liska’s garden during its migration to Mexico.

The monarchs who make the journey to Mexico in the late summer and early fall are instinctually different than those that came just before them, Liska said.

“In Kennett Square, we have five generations of monarchs that come through our gardens – May-June, June-July, July-August, August-September, and September-October,” he said. “The first four generations only get to live for two weeks, and they are only programmed to find a mate, mate and pass on the genetics of their DNA.”

The final generation can live up to eight or nine months, Liska said.

“That generation is programmed not to mate, but to fly all the way to Mexico,” he said. “They live not only from September and October, but to January and February of next year. When the weather changes, they know that it is time to fly back north, because the milkweed is now starting to sprout on all of the migratory routes back north.

“They may not fly all the way back here, but they will fly long enough to find a mate, often back to that region they left.”

During her presentation, Mayra Castillo from Casa Guanajuato Kennett Square spoke about the migration of monarch butterflies from Canada to Mexico, and shared the cultural significance of the monarch to Mexico and Mexican immigrants.  In Mexico, monarch butterflies are believed to spirits of people who have passed on, Castillo said, and when they arrive in the winter, it coincides with the Day of the Dead, Mexico’s most celebrated festival.

Because the monarch butterfly is able to travel freely between Mexico and the U.S., it has also become an important icon for those seeking to immigrate to the U.S.

To learn more about the monarch butterfly, visit

To learn more about Casa Guanajuato, visit, or call 610-335-6327.

To contact Staff Writer Richard L. Gaw, email [email protected].