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Locust Outbreaks
Name: Bonnie
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
Hi, I made a trip to Washington DC in the 80's as we passed through
Virgina, they were being invaded by large locust that looked like huge grasshoppers.
So many on the highway it was slippery on exit ramps, so loud you could not hear the
radio & it drowned out hte sound of the large trailer trucks passing by. What was
the reason for this & does it happen often? No one I talk to believes me.
Replies:
Virginia is home to several different broods of periodical cicadas, which
sometimes emerge in the numbers you describe. This site shows maps of brood
emergence for Virginia from 2002 forward. You can subtract 17 years from the
current decade dates and look at the map to see where you were in the resulting
past years.
http://pubs.ext.vt.edu/444/444-276/444-276.html
Periodical cicada are common throughout the eastern U.S. We had a major
emergence in northern Illinois in 2007.
J. Elliott
Grasshopper outbreaks tend to be cyclical and dependant on climate and other
insect populations. Often drought conditions will encourage grasshopper outbreaks.
Sunlight and high heat and humidity discourage important grasshopper pathogens and
are increase the speed of egg/nymph/adult development. Depending on what year it
was, 1988 had a massive drought over the U.S. These conditions could have made it
favorable for a grasshopper outbreak!
Grace Fields
When you mention that they were loud, I believe that you were seeing cicadas, not true
locusts (which ARE grasshoppers).
Some species of these tremendously loud insects have a very long life cycle: enormous
cohorts arrive every 17 years. There are so many that predators cannot eat them all
and cannot make a dent in their population. So huge numbers of cicadas mate and lay
eggs in a single summer, and the huge number of larvae grow and grow over the next 17
years, and then the adults erupt onto the scene once again, making the spectacle you
describe. I remember it well from my childhood in Maryland.
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
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Update: June 2012
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