Long live the monarch butterfly

It is a lot clearer than the water at Wakulla Springs that the monarch butterfly is in trouble and its numbers are declining. The total number of this most majestic butterfly has dropped to half of its numbers just a few years ago. In the winter of 1996-1997 the estimated number of monarchs overwintering in the Mexican reserves was more than a billion and they covered 51.82 acres of mountain tops. By the winter of 2013-2014 there were only enough monarchs to cover 1.65 acres.

Many monarchs spend the winter in large numbers to the Sierra Madre Mountains in Mexico. But most of the Monarchs that come down the eastern seaboard do not go around the gulf to Mexico, but winter along the coast of Florida and in the peninsula. We see monarchs near our coasts, particularly around St. Marks. Come spring, they all essentially reverse their direction and go north. It is an amazing trip. The butterflies stop to lay eggs on milkweed plants.

The egg, once fertilized, becomes a larva or caterpillar. The caterpillar of the monarch is voracious eater of the milkweed plant. And only the milkweed plant. Ultimately, the larva forms a pupa or chrysalis. Note that it is not a cocoon because it is not covered in silk. Metamorphosis takes place and some weeks later the adult butterfly emerges. That butterfly makes an additional leg on the trip north. The butterfly only lives a few weeks.

Since Monarchs travel about 50 miles a day, the process is repeated, and it takes several generations to fully return to the north. Their great- great- ever-so-great grandchild will return then to that same wintering ground when fall comes. No one knows really how the internal compass and memory guides the monarch to the same location generations after the grandparents last visited. It is a family tradition that skips many generations each year.

The sap of the milkweed is toxic to birds and insects, providing protection for the caterpillars. Birds vomit and spiders die. An exception is a bird in Hawaii that is very fond of the flavor of milkweed fed caterpillars.

What caused the collapse of the monarch? There are several causes, but the biggest cause is the industrialization of agriculture in the Midwest. Crops have been manufactured to be resistant to the powerful herbicide Roundup. This has increased crop yields. But milkweed is the only plant that monarch larva feed on, and Roundup kills milkweed. Through wider use of herbicides, and larger farms, milkweed is disappearing and so are the monarchs. Monarchs will die without milkweed.

You can help by planting milkweed plants. The seeds are inexpensive and you can even get them free on line. What a cool project for schools to undertake as part of their studies of nature and what we can do to be constructive.

Peter Ray is a professor of meteorology at Florida State University.