By Lisa T. Sarasohn / Special To The Washington Post

The American right has a newfound fascination with bugs. On the day of the Jan. 6 insurrection, the prominent Holocaust denier and white supremacist Nicholas Fuentes told the crowd, “What is happening in our country is parasitism.” During his presidency, Donald Trump often used the verb “to infest” in describing immigrants and people of color.

Yet, while this invocation of images of vermin might seem startling or harsh, such rhetoric isn’t new. Going back centuries, in fact, people have equated the verminous creatures who invade our bodies and our spaces with the marginalized and despised, with enemies and perceived inferiors. By associating the underclass with vermin, people in power substantiated their claims to superiority and justified their mistreatment and even murder of others.

For example, in 1658, the English naturalist Thomas Muffat declared “that the Blackmoors [of St. Thomas] there are full of Lice, but the white men are free of that trouble: All Ireland is noted for this, that it swarms almost with Lice.” The implication was that Black people and the Irish not only lived in filth but were categorically less than human. Such rhetoric framed politics as well. By legend, Oliver Cromwell at the Battle of Drogheda in 1649 ordered his troops to kill all the Irish, because “nits make lice.”

Associating people with bugs was dehumanizing because of new, classist ideas about hygiene. Before the 17th century, people accepted that having bugs on their bodies was a part of everyday life. But soon, educated people and people of means began to recognize that bugs were a source of disease, and they both worked to remove them and to use this effort to distinguish themselves from the lower classes. As a result they increasingly used verminous images as a weapon against the supposedly dirtier who were deemed unworthy and even vicious. Cleanliness became a necessary attribute of the civilized and cultivated.

These ideas and images became even more potent as Europeans conquered and colonized much of the rest of the world; and used them as tools for ingraining class hierarchies and justifying violence.

The powerful spoke about the powerless in terms of their tolerance of vermin, helping use these images to rationalize domination. In a 1791 account, Thomas Atwood, who had been chief judge of the island of Dominica in the Caribbean, maintained that Black people were too lazy to remove the “jiggers,” or chigoes, “an insect much like a flea,” from their bodies. Early modern accounts of distant places also commonly claimed that Africans and Eskimos ate lice, which demonstrated their bestial traits. Imperialism became seen as an essential strategy for pest control.

In the American colonies during the 18th century, one’s social standing became increasingly linked with a bug-free body and environment. A teenage George Washington, for example, dutifully copied the maxim, “Kill no Vermin, as Fleas, lice, ticks, etc. in the sight of others.” As people with resources worked to rid themselves of these creatures, they became markers of class. The expectation grew that these creatures would only inhabit enslaved people and members of the lower classes. At almost the same time, the world’s first professional exterminator set up shop in London, an entrepreneur capitalizing not only on new norms around hygiene but on clients’ concerns about the threat of social and racial embarrassment.

By the 19th century, there was an active debate among naturalists on the subject of whether people of different races attracted different species of lice. Charles Darwin was not a proponent of slavery; but that did not prevent him from asking the entomologist Henry Denny about whether human beings had different species of lice, which would demonstrate that not all people had a common evolutionary path. Denny had written that “some of the American Tribes” ate these “dainty morsels” as did the Hottentots of Africa. He told Darwin that South Americans’ hair was so filthy “as to render it unfit for the abode of even a louse.” Vermin were therefore incorporated into theories of social Darwinism.

By the end of the 19th century, vermin’s role in signifying human depravity was deepened by science’s discovery of their role in spreading disease. Charles Nicolle, director of the Pasteur Institute in Tunis, discovered that typhus was spread by lice in the clothes of patients infected with the disease. In 1930, the bacteriologist wrote, “Typhus presents itself as both a plague and a moral lesson. It tells us that man has only recently emerged from barbarity, that he still carries on his skin a disgraceful parasite such as brutes themselves carry.” He added, “The total suppression of the louse is not a question of hygiene, it is a question of civilization.” The implication? Civilized men did not have lice.

This idea continued to animate theories about racial hierarchy and power; and Nazi Germany revealed the deadly danger they held. Nazis were happy to reclaim civilization and cleanliness for the dominant race. Jews in particular, they argued, spread typhus in their lice-ridden clothes. In 1943, Reichsfürer Heinrich Himmler proclaimed, “antisemitism is exactly the same as delousing. Getting rid of lice is not a question of ideology. It is a matter of cleanliness. … We have only 20,000 lice left, and then the matter is finished within the whole of Germany.” For him, Jews were not human. They were parasites and thus, it was imperative to annihilate them.

The labeling of despised groups as either vermin-ridden or vermin themselves has persisted; with sometimes deadly consequences. During the Rwanda genocide in 1994, the Hutu branded the Tutsi as cockroaches, and 800,000 people were killed. More recently, during the 2016 Brexit debate in the United Kingdom, signs urged “Leave the E. U. No more Polish vermin.” In recent years, an Israeli rabbi was heard urging about Palestinians: “What we should do is go into those vermin pits and take out the terrorists and murderers. Vermin pits, yes, I said, vermin, animals.”

Likening groups of people to vermin is a deeply rooted practice of othering along lines of race, ethnicity or class, often used to demand and justify another group’s dominance. And being attentive to this language tells us far more about the people deploying it than those they seek to dehumanize.

Lisa T. Sarasohn is professor emerita of history at Oregon State University. She is the author of “Gassendi’s Ethics: Freedom in a Mechanistic Universe,” “The Natural Philosophy of Margaret Cavendish: Reason and Fancy during the Scientific Revolution” and the forthcoming “Getting Under Our Skin: The Cultural and Social History of Vermin.”