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Troubled species: Monarch butterflies' numbers drop

(MCT) NORMAL — A monarch butterfly flew over the home of Given Harper in late July.

There’s not much unusual about that, except the Illinois Wesleyan University biology professor said it was the longest he has ever had to wait for such a flyover.

“Last year, in late May, I had a caterpillar on the milkweed,” Harper said. “I can never remember not seeing a monarch until July 24.”

Others also have noticed the lack of monarchs this year.

“I’ve got a ton of milkweed and I’m not seeing any monarchs,” said Mary Jo Adams of rural Carlock, a master naturalist who is part of the Wild for Monarchs campaign of the Illinois Prairie Chapter of Wild Ones.

Kay Henrichs, a master gardener who lives in rural Bloomington with a yard full of butterfly-enticing plants, had seen only four caterpillars by early August when normally she would have seen 30 to 50.

So what’s happening? Several things — none of them good for the orange-and-black butterflies that are Illinois’ state insect.

Michael Jeffords, an entomologist with the Illinois Natural History Survey, said, “Last year’s drought had a twofold effect. Fewer monarchs were produced in the Midwest, and those that were had a tough time migrating to Mexico as they had a thousand miles of virtually nectarless landscape to cross in Texas and northern Mexico.”

Those that made it faced other challenges.

“The winter in the Sierra Madre mountains took a toll on the creatures, so far less made the journey back,” Jeffords said.

While last year’s severe weather took its toll, researchers also have noticed an overall decline, believed to be caused by factors ranging from loss of habitat in the central Mexico wintering grounds to agricultural practices in the Midwest and elsewhere.

Herbicide use, particularly in fields with genetically modified, herbicide-resistant corn and soybeans, has virtually eliminated from those fields the milkweed on which monarchs depend, according to Chip Taylor, a University of Kansas professor who is director of Monarch Watch.

Adult monarchs depend on a variety of plants for food, but they will only lay their eggs on milkweed. They aren’t just being picky. Substances in the milkweed make monarch caterpillars who eat their leaves toxic to would-be predators, a key to their survival.

“We’re not just losing monarch habitat; we’re losing pollinator habitat,” Taylor said. “What that means is we’re going to lose some plants out there.”

These plants produce fruits, nuts and berries eaten by other creatures — including humans.

Michael Toliver, a Eureka College biology professor who specializes in butterflies, calls monarchs “the canaries in the coal mine.”

Because butterflies have been studied in more depth than other insects that pollinate, “they’ll be the indicators of ecological decline,” Toliver explained.

Even for plants that don’t depend on insects for pollination, their disappearance can have an impact. Some, such as wasps, prey on other bugs that can damage crops, Toliver said.

“It’s the web of life and all that. You have to have a variety of pollinators,” Toliver said.

Life cycle

Monarchs are unique among butterflies because of their migratory habits. The monarchs that spend the winter in Mexico head north in the spring, laying eggs that turn into first generation butterflies, which continue northward. The first, second and third generation monarchs live only a few weeks. But the fourth generation — those that hatch in late summer or fall — become the so-called “Methuselah” generation, the monarchs which make the journey to Mexico and live six to nine months.

“They’re absolutely beautiful organisms, so brightly colored,” Harper said. “I marvel at the ability of an organism to fly a couple of thousand miles to a place they’ve never been before.”


©2013 The Pantagraph (Bloomington, Ill.)

Distributed by MCT Information Services

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