FEBRUARY
2014

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Flies in the face of fashion

What's Buggin You Now?

 

 

 

02-13-14

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End of the Monarch Reign?


Monarch butterfly on Milkweed
Monarch butterflies deposit their eggs on milkweed plants.
Photo credit: Betty Hall

For hundreds, maybe thousands, of years, monarch butterflies flapped and floated across prairies and through woodlands of the Eastern part of the United States. Then, as trees and native grasses fell before the ax and plow of the pioneers, an agricultural patchwork of pastures, corn and hay fields, roadsides and fencerows emerged. But unlike the bison and the bobcat, the monarch butterflies soldiered on.  

Each spring the bronze-colored butterflies with the distinctive black-line markings begin a northward trek. Along the way, the butterflies sip nectar, mate and deposit eggs on milkweed plants.

Come fall, second- and third-generation descendents of the spring monarchs head south. Some start as far north as the southern regions of the Canadian provinces of Quebec, Ontario and Saskatchewan.

These fall monarchs set off on a very long and dangerous journey. Some have to travel more than 2,000 miles, with only favorable winds and wing muscles to carry them along. They all head to a little spot, a few square miles, in the mountains of central Mexico. These fall-migrant monarchs have never been there, but it's a place where wintering monarchs have avoided the lethal cold and snows of northern climates for untold generations.

Because of their size, coloration and migration habit, the monarch is one of the most recognized and most admired of the butterfly species. Many books and poems extol the virtues of this insect, which is native to North America.

 In spite of the adulation of and the press about the monarch, the facts regarding its migration were unknown for many years. Relative to the monarch butterfly, historical entomologist, J. H. Comstock of Cornell University wrote in his 1895 book, "Manual for the Study of Insects": "It is believed, however, that the species dies out each year in a large part of the Northern States, and that those butterflies which appear first in this region, in June or July, have flown hither from the South, where they hibernated in the adult state. In the extreme South they fly all winter."

The research to finally unravel the mystery of the monarch migration was conducted by University of Toronto zoologist Fred Urquhart and his wife, Norah. Beginning in 1937, the Urquharts reared monarch butterflies and, with the help of a cadre of "citizen scientists," attached bands to the wings of the insects and tracked their southward movements. The banded-monarch trail always seemed to end in Texas.

But then in 1975, naturalists Kenneth Brugger and his wife, Cathy, who were working with the Urquharts, were able to pinpoint that millions of monarch butterflies were taking refuge in the mountains of Mexico during winter months.

But now the population of monarch butterflies seems to be on the decline. As is the case with all insects, life of a monarch butterfly is a perilous journey. But to monarch watchers, two factors controlled by humans seem to be at the forefront when it comes to success of the butterfly.

The first is the maintenance of the habitat in the overwintering sites in Mexico. These sites provide the combination of temperatures, tree resting sites and available water that the insects need for winter survival. But the areas have come under logging pressure and are declining in size. Some of the sites have been designated as nature preserves in order to save the habitat.

The other major problem for the monarch butterfly is the availability of caterpillar feeding sites. Monarch caterpillars need milkweed plants as a food source. Because of modern agricultural technology, a weed plant such as the milkweed is now easily controlled, compared to 20 years ago. As a result, milkweed populations are probably at the lowest level in history. This means that monarchs can't find plants on which to lay eggs and, as a result, butterfly populations decline.

It is obvious that any "save the monarch" campaign must be based on programs dedicated to providing milkweed plants. This can be done individually in home garden sites or in state-mediated programs to maintain milkweeds in state parks and in non-mowed areas of interstate highways and other roadways.

Anyone have any good slogans for this campaign? How about "Feed a Monarch, Plant a Milkweed"? Or "Milkweeds for Monarchs." 


 

Writer: Tom Turpin
Editor: Olivia Maddox