|On Six Legs
By Tom Turpin
The term “globalization” is widely used to describe what is happening to the world in the first decade of the 21st century. It is all about technological, economic and cultural exchanges made possible by modern communication and transportation. The result is more trade, investment and migration among countries than ever before.
For a variety of reasons, not all humans think that globalization is the greatest thing since sliced bread. One disadvantage of human globalization is that it has become easier and easier for insects to tag along. Hitchhiking insects can mean that some of the stowaways end up staying. Over the years, a few species of globetrotting insects have become major pests here in the United States.
Insects, like all other animals, have a biological imperative to move. Such movement allows animals to establish populations in areas where they have never been found before. In ecological terms, this means the animal has increased its range. In some instances, animals move back into areas where their populations were once found but, for some reason, no longer exist. Examples include areas where floods or volcanic eruptions eliminated animal populations.
Insects move by crawling, walking or flying. Crawling and walking are not good ways for small insects to cover long distances. Flying, on the other hand, can allow insects to travel long distances. The monarch butterfly can fly up to 3,000 miles as it moves from summer breeding grounds in Canada to the mountain locations in Mexico, where it spends the winter. But, in the insect world, the annual trek of monarch butterflies is the exception to the rule. Most insect travelers, even if they use the power of flight, do not travel long distances. To most insects, far from home is a matter of feet or yards, not miles.
Insect flight that covers long distances, including the marvelous journey of the monarch butterfly, is often wind-assisted. A few insect species even fly skyward in a biological process known as “towering” and end up being carried by weather fronts. These insects are kept aloft by the wind until they are dumped like rain hundreds of miles from where they began the journey. Many small insects, such as leafhoppers and aphids and even a few larger moths, get to see the old U.S.A., not in a Chevy, but courtesy of one of nature’s zephyrs.
Some insects have managed to travel long distances by tagging along with humans. Insect globalization has been a team effort, sometimes on purpose. For instance, the well-known honey bee was carried to North America from Europe by early settlers. The honey bee has been a valuable introduction.
The gypsy moth was also intentionally transported to our shores. This insect was imported from Europe in 1869 as part of an experiment to improve silk production in the United States. The experiment didn’t pan out, the insects escaped their confinement, and the French researcher who brought gypsy moths here went home. It is a similar story with the Africanized honey bee. But, this time, the story began in Brazil. After their escape, the bees began moving northward and are now found in the United States in the Southwest and in Florida.
But, mostly, insect travelers arrive by accident. Take that scourge of the lawn and garden, the Japanese beetle. This insect arrived in New Jersey about 1916 as grubs in the soil around nursery rootstocks coming from, you guessed it, Japan. Since then, it has been westward ho under its own power and, on occasion, hitching a ride on cars, trains and even planes.
The European corn borer showed up in broomcorn from Italy or Hungary, probably about 1908. Hessian flies, pests of wheat, came ashore in straw bedding used by Hessian troops during the Revolutionary War and were first noted in Long Island in 1779. The Anopheles mosquitoes that are the vectors of malaria and the organism that causes the disease came to America on slave ships.
More recently, the emerald ash borer arrived in the port of Detroit in 2002. The insect arrived as larvae, coming from the Orient in wooden ballast, which was dumped onto shore after the ships were unloaded. These insects emerged and infested ash trees in the vicinity. Now, by expanding their range, the emerald ash borer is a threat to all ash trees in the United States. Hey, globalization is not just a human thing.
This farm news was published in the March 15, 2006 issue of Farm World.