OCTOBER
2009

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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10-08-09

Download the audio of On Six Legs: MP3, WMV.

When Insect Hordes Wreak Havoc

Every fall an insect called the soybean aphid takes a little trip. Like many aphids the soybean aphid has two host plants -- one where it spends the summer and another where it spends the winter. In the case of the soybean aphid, and you might have already guessed this, the summer host plant is the soybean.

As winter approaches soybean aphids develop winged forms that take flight in search of buckthorn plants. The winged aphids lay eggs on the buckthorn plants. These eggs then spend the winter on the buckthorn and when spring arrives the eggs hatch, and a new crop of soybean aphids begins to develop.

Normally, the soybean aphids are largely unnoticed as they make their annual fall pilgrimage. After all, soybean aphids are small insects, about the size of -- or a bit smaller than -- the familiar fruit flies. So, in general, people don't pay much attention to small flying insects that are often lumped under the generic term of gnat.

While a gnat or two might not become an issue for most people, high numbers of these small flying insects will attract attention. And so it was this year with the soybean aphids.

The aphids were flying around in such numbers that people were getting them in their eyes and ears. Bicyclists and joggers were sucking the insects into noses and mouths. Windshields of cars and helmet visors of motorcyclists literally became covered with smashed aphids.

Almost any daytime outdoor activity during the weeklong flight period resulted in aphid and human encounters of the closest kind. Aphids even plagued the Purdue University marching band practices. I guess it's hard to concentrate on music and marching formations with aphids in your eyes and nose, or in your trumpet, for that matter.

But aphids aren't the only insects that occasionally show up in large numbers and interfere with human activities. For instance, on Oct. 6, 2007, a major league baseball game between the New York Yankees and the Cleveland Indians was suddenly inundated by hoards of flying midges. These small biting insects were attracted by the lights of the stadium and made life miserable for the players. A Yankee pitcher was especially affected and threw two wild pitches while besieged by the midges and proclaimed that the insects "bugged him." Because the Yankees lost the game, one newspaper headline proclaimed "Midges 1, Yankees 0."

Another insect that sometimes creates havoc with massive numbers is the mayfly. Mayflies are insects that are aquatic in the immature stages. These insects sometimes emerge from the water in numbers great enough to be picked up on Doppler radar. The adult of the mayfly only lives for about a day, so the carcasses of the dead insects accumulate on bridges in similar fashion to the accumulation of snow during a winter storm. In fact, many are the reports of the need to use snowplows to remove the mayflies from bridges to prevent auto accidents caused by poor traction.

In July 2006, a bridge in Pittsburgh was closed for an hour while the dead mayflies were removed. In the same year, bridges over the Mississippi River near Lacrosse, Wis., were inundated with mayflies that were piled into "drifts."

Mayfly emergences also plague Europe. In 2009 the Bavarian town of Schwandorf was forced to close a bridge overnight because of mayflies. According to reports, "the slimy film is as slippery as black ice in winter." Snow shovels and fire hoses were used to clear the road. In 2007 mayflies emerging from the Danube River were attracted to lanterns on bridges in such numbers that the scene was described "like standing in a snowstorm."

While hoards of flying insects seem to attract the most attention, at least one caterpillar is known to turn a few heads when it migrates. These are the armyworms, so named because they march like an army from one field to another. The armyworms are moth caterpillars, and they move "in mass" from a field once they have devoured the foliage. The hungry march sometimes crosses roadways where caterpillars by the thousands get smashed and result in slick road conditions, complements of greasy caterpillar guts.

Whether on the fly or on the march, hoards of tiny insects do attract attention. And generally that attention does little to create positive feelings among humans for the insect world.

 

 

Writer: Tom Turpin
Editor: Olivia Maddox