Ornamental Separator

A Fiendish Fly

An insect became the object of American fears — and Thomas Jefferson’s attention

Politics wasn’t the only matter over which Thomas Jefferson obsessed. When it came to science and, more specifically, natural history, he could be just as riveted.

In fact, Jefferson spent an inordinate amount of time and energy studying, and pontificating about, Mayetiola destructor — the Hessian fly.

The Hessian fly appears at the onset of the American Revolution. According to records dated 1776, this new pest was attacking the wheat crop near Long Island, New York. The insect’s appearance coincided with the arrival there of Hessian troops to join the Crown’s effort to suppress the budding revolution.

At first, the pest attacks were scattered and sporadic. But within a decade, the fly was traveling south and west — at a rate of 20 miles a year by Jefferson’s reckoning — spreading alarm among the population.

Rumors spread that this still unnamed insect had come over in the straw beds of the Hessian mercenaries, a theory that is plausible but unsubstantiated. Soon the rumors became even more sinister: A biological weapon was in play, a scheme in which “the Hessians have brought over thousands of little insects, on purpose to destroy this country,” according to a 1788 publication containing observations about the pest.

No evidence but no matter. It might have happened that way, and that was enough for George Morgan, a land developer, a gentleman farmer and a member of the American Philosophical Society, to recognize that dubbing the fly a Hessian of any sort would tap into the hatred-of-the-invader mindset that to this point had been reserved for human intruders. In August 1788, Morgan wrote:

The name of Hessian Fly was given to this Insect by myself.... 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. 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.

Though Jefferson may have learned of the fly earlier, the first documented evidence comes from a 1787 letter he received in Paris, where he was serving as an envoy. A year later the American Museum magazine painted a dreary picture in which farmers “dread its [the Hessian fly’s] approach...the whole continent will be over-run — a calamity more to be lamented than the ravages of war.” That same year William Hay, a director of public buildings in Richmond, wrote Jefferson of the Hessian fly’s presence in Virginia, noting, “The Damage is done...the little Enemy dwells in safety.”

Matters unfolding in England also caught Jefferson’s attention. The Privy Council committee on trade, which was stocked with members still seething over the lost war, was warned of the dire consequences of the Hessian fly should the government continue to import wheat from America. Headed by Joseph Banks, president of the Royal Society of London, the council recommended to King George III that American wheat imports be banned to circumvent “a calamity of much more extensive and fatal consequences than the admission of the plague.”

What was especially galling to Jefferson was that while there was scant evidence either way about whether the fly larvae would survive the trip to Britain, Banks set an impossible standard: “positive proof that no danger whatever exists” — reinforcing the notion that this was retribution for a lost war.

Thomas Paine wrote Jefferson that the ban “was only a political manoeuvre of the Ministry.” Jefferson concurred. He wasn’t worried about the effect of the ban per se, as England imported only a small proportion of America’s wheat exports, but the ban might scare other countries like France, which imported much greater quantities. Jefferson railed that the report was little more than a “libel on our wheat...which can have no object but to do us injury by spreading a groundless alarm in those countries of Europe where our wheat is constantly and kindly received. It is a mere assassination.”

The ban was rescinded less than two years later, but in Jefferson’s eyes the damage had already been done.

Jefferson had his hands full when he returned to the United States. Washington had appointed him the country’s first secretary of state, and he was also vice president of the American Philosophical Society. Both positions would play a role in his growing connection to the Hessian fly. In 1791, Jefferson created and chaired a society committee “for forming the natural history of the Hessian fly” and determining “the best means of preventing or destroying it.” Though no records from the early meetings of this committee exist, Jefferson would soon get the chance to gather some of the Hessian fly data himself.

Stressed from the never-ending arguments with Federalists led by Alexander Hamilton, and suffering migraines, Jefferson jumped at the opportunity in the spring of 1791 when James Madison suggested that they take a monthlong excursion to the lands and lakes of New York, Connecticut, Vermont and New Jersey. By Madison’s description, the journey would be for “health recreation and curiosity.” Jefferson saw it as a chance not just to relax but also to survey farmers about the Hessian fly along the way.

Jefferson and Madison decided to meet in New York City on May 19 and to commence from there. That was a mistake. The presence of two prominent anti-Federalists in what was a hotbed of Federalism, as well as the adopted home of Hamilton, Jefferson’s nemesis, set the rumor mill turning. Surely the secretary of state was not really interested in rest and relaxation — that was just a cover. Hamilton’s allies saw the visit as a step to undermine their leader, and, more generally, the Federalists.

“Delenda est Carthago [Carthage must be destroyed] I suppose is the Maxim adopted with respect to you,” New York State Assemblyman Robert Troup wrote to Hamilton, his friend and King’s College roommate. “If they succeed they will tumble the fabric of the government in ruins to the ground.”

Hamilton’s son John wrote of the “pretext of a botanical excursion to Albany” covering up a Jeffersonian scheme against his father’s party. Though the reason isn’t clear, the British consul general John Temple was convinced that Jefferson and Madison had “gone to the Eastern States, there to proselyte as far as they are able to a commercial war with Great Britain.” Neither Jefferson’s nor Madison’s journals during their trip nor their writings afterward even hint at a plot against the Federalists or a commercial war against Britain.

Instead, Jefferson’s journals show him to be a polymath. He rated each of the 28 inns they stayed at and made dozens of entries on the flora and fauna of the region. His interest in American Indian culture was fed when he visited an Unquachog Indian settlement of “about 20. souls.” Learning that only three persons of this tribe could still speak its language, he spent a day talking with two women from the tribe and deciphering the English equivalent of almost 300 Unquachog words.

Jefferson’s journal also shows that the Hessian fly was front and center in his mind. Between May 24 and June 18, he compiled a six-page document, “Notes on the Hessian Fly.” His first entry was logged near Poughkeepsie, where a farmer told him that “the Hessian fly remains on the ground among the stubble of the old wheat.” Twenty miles away, he learned, “the fly came first in 1787.... and destroyed the crops.” He made page after page of such entries, one of the last while visiting Long Island where “this insect first appeared.... The Hessians were stationed here in 76.”

When Jefferson returned to Philadelphia, he and his committee wrote up a “Circular on the Hessian Fly,” which was printed in newspapers around the country. It was a plea for more information, with nine sets of questions, including “In what year, and at what time of the year, was this animal observed for the first time?” The circular spurred a few replies. David Redick, a lawyer and surveyor in Washington County, Pennsylvania, wrote, “The fly appears...about Six or Seven Miles South of this Town.” Joseph Moore, a Pennsylvania physician, wrote that the flies’ “depredations do not appear to be confined to any Particular soil,” and John Sheppard noted that “it seems most Injurious to wheat sown on a low wet Soil.”

But the responses were not sufficient for Jefferson’s committee to produce a report, and the committee dissolved. Jefferson had his own unhappy encounter with the Hessian fly at Monticello, when it invaded his fields around 1811.

But as his passions drifted elsewhere, the insect gradually lost his attention. His political duties would grow only greater — and with that, his obsession with the stubborn pest came to an end.

The Hessian fly is believed to have been transported from Asia to Europe, where it plagued farmers in wheat-producing countries. (Illustration by Patrick Wright)

Lee Alan Dugatkin is a professor of biology and a College of Arts and Sciences distinguished scholar at the University of Louisville. He is an evolutionary biologist and a historian of science and the author of numerous books, including Mr. Jefferson and the Giant Moose: Natural History in Early America, which recounts the origin and evolution of debates about natural history in America.

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