After doing the research for our novels about Meriwether Lewis and William Clark, I can’t imagine a richer historical setting than early America. And though we included a lot of the period details that captivated us, inevitably there were some characters that ended up on the cutting room floor. Among these was the Hessian fly, which was ravaging America in 1794, the year that Lewis and Clark met and in which our novel The Fairest Portion of the Globe is set.
The notorious pest was Mayetiola destructor, known also as the barley midge, and it suddenly appeared in the farm country of New York, New Jersey, and Connecticut in the late 1770s as the Revolutionary War raged. This tiny insect, scarcely visible to the naked eye, was capable of chewing through entire fields of wheat in a matter of days and was soon dubbed the “Hessian fly” after the notorious mercenary German soldiers hired by the British crown. Many believed that the fly had arrived in the United States in the filthy straw bedding of the Hessians. That is unprovable, but most scientists today believe the fly did arrive in straw, probably horse forage, shipped in by the British for use in putting down the revolution.
George Morgan, a revolutionary officer and farmer near Princeton, left a vivid description of the fly, which carried out its destruction in the larval stage:
…White Worms which after a few days turn of a Chestnut Color — they are deposited by a Fly between the Leaves & the Stalk of the green Wheat, & generally at the lowermost Joint, and are inevitable Death to the Stalks they attack.
Pending a scientific explanation, the destruction caused by the fly was an occasion for soul-searching. The Reverend Timothy Dwight suggested that “nothing can more strongly exhibit the dependence or littleness of man than the destruction of his valuable interests by such minute, helpless beings, nor can anything more forcibly display the ease with which his Maker punishes his transgressions.”
After the Revolution, the fly embarked on a relentless flight westward, moving at a rate of about 20 miles per year. By the 1790s, American wheat exports had plummeted even as revolutionary France ramped up demand. Many of the big names in early American science worked to combat the fly, including Thomas Jefferson. In May 1791, Thomas Jefferson (then U.S. Secretary of State) and his colleague and close friend, James Madison, took a leisurely trip through New England where they mixed hiking and fishing with serious business matters. Jefferson had agreed to chair a special committee of the American Philosophical Society that would gather scientific data about the fly and develop methods of fighting it. During his trip he conducted interviews with farmers and townsfolk about their experiences and observations, and even traced the origin of the plague back to a spot in present-day Brooklyn.
Jefferson continued to fit his research in with his work as America’s top diplomat. In the summer of 1792, he pupated live Hessian flies, watched them hatch and lay their eggs, and examined them through his microscope. Unfortunately, Jefferson was then caught up in his intense feud with Alexander Hamilton and then in the Citizen Genet affair, which led to his resignation the following year. He never again took up his involvement with the fly’s saga, though that didn’t stop Federalists from lampooning him as an eccentric who interrupted the public business to write “dissertations on cockroaches.”
The fly moved south and west, wreaking more destruction. Between 1796-99, America exported virtually no wheat at all thanks to the fly’s depredations. Though Jefferson was no longer in the lead, the fly’s menace proved the kick-starter for the development of American entomology. By the early 19th farmers were starting to adapt their practices to combat the fly, specifically by delaying their fall plantings until after the fly was done spawning, planting varieties of wheat observed to be fly-resistant, and diversifying to other crops, especially corn and rye. The Hessian fly continues to munch on wheat to this day, never eliminated, only controlled.
For more reading, check out these excellent articles:
Hessian Fly (Monticello)
Seeing the Light: A Close Look at 18th-Century Optics (Colonial Williamsburg)