A few years before Thomas Jefferson sat down to write the Declaration of Independence in the summer of 1776 at a second-floor rented apartment in Philadelphia, a mysterious pest began to devastate farmers’ wheat crops in Long Island, New York.
Soon it spread to New Jersey. In its larval stage the tiny white worm munched its way to adulthood by feeding on wheat, barley and rye.
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“It began in Long Island and Brooklyn, and they could sit and watch as the insect moved further west and further south,” said Lou Masur, professor of American history at Rutgers University. Masur said the fly worried farmers, many of whom, like Jefferson, were also delegates to the Continental Congress.
“They are concerned, deeply concerned because wheat is critical not only to domestic production but to exports,” Masur said.
After the American Revolution, Jefferson would embark on a mission to understand and document one of the country’s first invasive species. No larger than a gnat, it spurred suspicions of biological warfare, threatened the new nation’s economy and inspired a citizen science project that in one historian’s assessment epitomized American “optimism in the power of collective scientific work.”
In some ways this story begins in August 1776, when thousands of German soldiers known as Hessians arrived on Staten Island to fight against the Continental Army. Paid by the British, the Hessians sparked fear and resentment among the colonists — helping to rally more American colonists to the cause.These soldiers were so hated, they were mentioned as one of the 27 grievances listed by Jefferson in the Declaration of Independence. Jefferson condemned King George III for hiring about 30,000 of these “mercenaries” who “compleat the works of death, desolation and tyranny.”The soldiers raped women and pillaged farms throughout New Jersey before getting routed by George Washington’s troops during the Battle of Trenton, who made the famous crossing of the Delaware River on Christmas Eve 1776.The hated fly that destroyed farmers’ wheat crops soon became linked with the hated German soldiers. Rumors spread that the pest hitched a ride to America through the straw bedding of Hessian soldiers. Some thought it was a deliberate attempt to sabotage the rebellion. In theory, the insect could have arrived this way, but there is no evidence linking its origins to Germany or that it was a piece of biological warfare employed by the Hessians or the British.But the story stuck.
How the Hessian fly got its name
After the war, a “gentleman farmer” and slave owner from Princeton named George Morgan looked out over his devastated crops and decided the pest needed a name — in fact, a very bad name.
Morgan explained in a 1788 letter to Britain’s Consul General to the U.S. John Temple that he wanted everyone to connect the destruction and violence by Hessian soldiers of New Jersey’s farmsteads with the devastation wrought by the fly.
“The name of Hessian Fly was given to this Insect by myself & a Friend early after its appearance on Long Island, as expressive of our sentiments of the two Animals – We agreed to use some Industry in spreading the name to add, if possible to the detestation in which the human and insect [were] generally held by our yeomanry & to hand it down with all possible Infamy to the next Generation as a useful National Prejudice,” he wrote.
“It is now become the most opprobrious Term our Language affords & the greatest affront our Chimney Sweepers & even our Slaves can give or receive, is to call or be called Hessian.”
“It’s a very powerful piece of rhetorical propaganda, out of the rage that the revolutionaries felt of those 30,000 Hessian soldiers who fought for the British during the war,” Masur said.
That same year, Morgan wrote to George Washington after the fly had reached Philadelphia. Calling it “alarming to farmers,” he described in detail his experiments to save his crop.
‘A libel on our wheat’
In 1788, Britain banned wheat imports from the U.S. because of the Hessian fly. Thomas Jefferson was furious, calling it a “libel on our wheat” and saying it was in retaliation for America winning the war.
Jefferson soon got involved as a member of the American Philosophical Society — which spearheaded scientific research into the Hessian fly.
The American Philosophical Society — created by Benjamin Franklin in 1743 to “promote useful knowledge” — still exists today in a faux-colonial building near Independence Mall. It’s here where millions of colonial-era documents are stored, including official minutes from the American Philosophical Society meetings.
Adrianna Link, the society’s history of science curator, opens a restored sheepskin bound volume of minutes from 1787 to 1793.
“I want to show you too just so you can see, these are the official APS minutes from 1787 to 1793,” she said.
“These are really incredible accounts that represent the conversations that would have been happening at the society during the time,” Link said. “So here, this is an entry from April 15, 1791 … ‘on motion of Mr. Jefferson resolved that a select committee be appointed to collect and communicate to the society materials for forming the natural history of the insect usually called the Hessian fly.’”
The nation’s first citizen science project
In 1791, Jefferson and James Madison set out on an expedition, traveling through New Jersey and New York to survey farmers, asking them to record their experiences and observations of the Hessian fly.
While they didn’t get the amount of responses they expected, Link said their attempts at employing citizen science was a uniquely American — as opposed to British — way to solve the problem.
“I don’t think you get as many people in the Royal Society conversation who are gentlemen farmers sending in their letters about pest sightings of the day,” Link said. “That I think is distinct. There’s this kind of optimism in the power of collective scientific work.”
Link said Jefferson’s obsession with the fly was two-fold: serious risks to the nation’s budding independent economy and pride that American science — or what was then referred to as natural history — could be just as effective as European.
“I think Jefferson being sort of the driving force in this is telling because he did see science as being a mechanism through which to build the nation. So the fact that he was really preoccupied with the Hessian fly tells you something,” she said.
By 1811, the Hessian fly had traveled south to Jefferson’s fields at Monticello — destroying one-third of his wheat crop.
Today, the consensus is that the pest was never even in Germany.
The Hessian fly originated in the fertile crescent in North Africa and the Middle East — the same place where wheat originated, said David Buntin, professor of entomology at the University of Georgia.
“The fact is, like a lot of these invasive pests, we really don’t know exactly how they get here,” Buntin said. “We just know when they show up.”
Buntin, who has spent four decades researching ways to keep ahead of the Hessian fly’s adaptations and protect Georgia’s wheat crops, said the pest is manageable but can still be devastating when it does hit.
“I’ve always felt honored to be working on an insect that Thomas Jefferson worked on,” Buntin said. “I’m in good company. There’s not very many insects that a former president has spent time working on.”
The tiny larvae emerge at the base of the plant several times a year, and in some areas of the country climate change could be making it worse.
The solutions today aren’t that different than they were 250 years ago — find and develop more resistant strains of wheat, and time fall planting to avoid egg laying. Buntin said in addition to being one of the first invasive species documented in the U.S., the Hessian fly gave rise to one of the first documented resistant plant species.
The Princeton farmer George Morgan would be happy to know that he succeeded in passing down his “useful National Prejudice” to more than the “next Generation.”
Almost 250 years later, everyone, scientists and farmers alike, still call it the Hessian fly.
