Friday, November 22, 2013

Globetrotting Butterflies

Red admiral (Vanessa atalanta) on snake root
© Beatriz Moisset
Name a lovely butterfly found throughout North America and also an intrepid traveler, capable of crossing the entire continent from north to south. You probably had the answer before I completed my question. The monarch is the best known butterfly in the United States. Its migration from Mexico to Canada and back, involving several generations and taking months each year, fascinates us all.

Painted lady (Vanessa cardui) on mountain mint
© 2013 Beatriz Moisset
Now, name another lovely butterfly just as widely distributed and also a remarkable migrant. Can you name just one? What about two? Now, what if these two butterflies could be seen in Africa, Europe and Asia in addition to North America? In those continents they would travel from Africa to Europe or from South Asia to farther north. The two species I refer to bear unusually pretty scientific names, Vanessa atalanta and Vanessa cardui. We know the first one as red admiral and the latter as painted lady.

Red admiral caterpillar feeding on nettle
© Beatriz Moisset
As we know, the monarch caterpillar feeds only on milkweeds. The Vanessa caterpillars also have some favorite food plants; however they can dine on members of several other plant families as well. The red admiral prefers nettles and the painted lady goes for thistles. In fact the scientific name cardui comes from cardus, which means thistle in Latin. I hope you have an assortment of native nettles and thistles in your garden for the benefit of these delightful visitors and their families. If you don’t, they can resort to other members of the aster, pea or mallow families.

Red admiral caterpillar
safe and sound inside a nettle leaf
© Beatriz Moisset

These two species of butterflies are just as beautiful and adventurous as the monarch, so their lack of popularity surprises me. Perhaps all they need is a little publicity. They are brightly colored in black, orange and white, and slightly smaller than monarchs. If there was a beauty contest I would probably vote for the gorgeous red admiral. I would also insist in calling it by its sweet scientific name, Vanessa atalanta.

I already mentioned that you can see them, at least part of the year in your area, wherever you live. You may have already noticed them in your wildlife garden. Perhaps you even thought you were seeing a monarch, a common mistake. I have watched them nectaring on asters, coneflowers, snakeroots and mountain mints among others.
Red admiral on cone flower. ©  Beatriz Moisset
We happen to know a lot more about the comings and goings of monarchs than of painted ladies and red admirals. Maybe this will change in the future because research continues. In fact, you can contribute your observations if you are interested in being a citizen scientist by participating in the Iowa State University program at the "Red Admiral and Painted Lady Research Site". In Europe the "Insect Migration & Ecology Lab" is also following the red admiral migration in that area.

American lady (Vanessa virginiensis)
. © Beatriz Moisset
We know that they fly north in the spring and south in the fall. How far they go or whether some hunker down and spend the winter in colder areas is not known. Years ago it was thought that the ones that migrated to northern latitudes never made it back, just died without descendants; but that may not be the case. The migration of the painted lady in Europe is better studied. There, it is capable to fly in the fall all the way from England to North Africa, a deed as impressive as that of the monarch.

I hope you are as intrigued as I am about these globe trotting butterflies. This may inspire you to join the efforts to unravel the mystery of their migration and also provide habitat for them. Next year, enjoy your Vanessa butterflies that come to call.

Monarch butterfly (Danaus plexippus) for comparison
© Beatriz Moisset


Friday, November 8, 2013

The Monarch's Breadbasket

Monarch on milkweed © Beatriz Moisset
For years the so called Corn Belt has been our breadbasket, as well as that of the monarch butterfly. Despite farmers' efforts to remove all weeds, common milkweeds proved well adapted to corn fields and prospered year after year, encouraged, rather than hindered by annual plowing. Other milkweeds, with different habitat demands lost ground to the point of becoming endangered. But common milkweed (Asclepias syriaca) and its rich accompanying fauna, including the monarch butterfly, continued to do well.

Monarch caterpillars need milkweed,
which used to grow in relative abundance
in corn fields of the Midwest
© Beatriz Moisset
Recently this changed with the advent of genetic modifications that make corn and other crops resistant to weed killers called glyphosates, mainly Roundup. Nowadays, approximately 90% of corn and soy seeds are genetically modified. Now farmers can use Roundup freely on these resistant crops. This radical change in farming practices is having unpredictable impacts in ecosystems. One effect of herbicides used in this manner is that it finally became possible to wipe out populations of common milkweed that previously had managed to prosper in cultivated fields and along field edges. What is good for the farmers may prove devastating for the monarchs.

According to some recent studies, most of the monarchs in Canada and the East Coast (fourth and fifth generations) are descended from the ones born in the Corn Belt (second and third generations). It seems that the weakest link in the chain is the Midwest where herbicide-resistant crops plus herbicides are decimating the common milkweed. Trying to strengthen the other links may be futile.

Monarchs used to be numerous in Cape May, NJ,
during fall migration, but no more despite abundant nectar
© Beatriz Moisset
Our milkweeds and nectar plants, here in the East, are almost devoid of monarch butterflies. The same thing applies to the oyamel forests of Mexico where overwintering monarchs used only a small fraction of the available habitat last year (2012).

Common milkweed patch in Southeastern Pennsylvania
Very few monarch caterpillars this year, 2013
© Beatriz Moisset
 If we want to save the monarchs, we need to save their breadbasket by stopping the use of herbicides in our own breadbasket.

Benbrook, C.  Impacts of genetically engineered crops on pesticide use in the U.S. -- the first sixteen years. Environmental Sciences Europe (2012)
Brower, L.P. Understanding and Misunderstanding the Migration of the Monarch Butterfly (Nymphalidae) in North America: 1857-1995. Journal of Lepidopterists' Society. First observations page 306. Mexico, pages 312-213
Pleasants, J., Oberhauser, K. Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population. Insect Conservation and Diversity (2012)