How the Gypsy Moth Came to America

Trouvelot's legacy.
Trouvelot's legacy. Gypsy moths continue to thrive and spread in the U.S. © Debbie Hadley, WILD Jersey
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How Leopold Trouvelot Introduced the Gypsy Moth to America

Trouvelot's home on Myrtle St. in Medford, MA.
Trouvelot's home on Myrtle St. in Medford, MA, where imported gypsy moths first escaped. From "The Gypsy Moth," by E.H. Forbush and C.H. Fernald, 1896.

Sometimes an entomologist or naturalist makes his mark on history unintentionally. Such was the case with Etienne Leopold Trouvelot, a Frenchman who lived in Massachusetts in the 1800's. It's not often we can point the finger at a single person for introducing a destructive and invasive pest to our shores. But Trouvelot himself admitted that he was to blame for letting these larvae loose. Etienne Leopold Trouvelot is the culprit responsible for introducing the gypsy moth to America.

Who Was Etienne Leopold Trouvelot?

We don't know much about Trouvelot's life in France. He was born in Aisne on December 26, 1827. Trouvelot was just a young adult when, in 1851, Louis-Napoleon refused to accept the end of his presidential term and seized control of France as a dictator. Apparently, Trouvelot was no fan of Napoleon III, because he left his homeland behind and made his way to America.

By 1855, Leopold and his wife Adele had settled in Medford, Massachusetts, a community just outside of Boston on the Mystic River. Soon after they moved into their Myrtle Street home, Adele gave birth to their first child, George. A daughter, Diana, arrived two years later.

Leopold worked as a lithographer, but spent his free time raising silkworms in their backyard. And that's where the trouble began.

How Leopold Trouvelot Introduced the Gypsy Moth to America

Trouvelot enjoyed raising and studying sillkworms, and spent the better part of the 1860's determined to perfect their cultivation. As he reported in The American Naturalist journal, in 1861 he started his experiment with just a dozen polyphemus caterpillars he had collected in the wild. By the following year, he had several hundred eggs, from which he managed to produce 20 cocoons. By 1865, as the Civil War came to an end, Trouvelot claims to have raised a million silkworm caterpillars, all of which were feeding on 5 acres of woodlands in his Medford backyard. He kept his caterpillars from wandering off by covering the entire property with netting, stretched across the host plants and secured to an 8-foot high wooden fence. He also constructed a shed where he could raise early instar caterpillars on cuttings before transferring them to the open air insectary.

By 1866, despite his success with his beloved polyphemus moth caterpillars, Trouvelot decided he needed to build a better silkworm (or at least cultivate one). He wanted to find a species that would be less susceptible to predators, as he was frustrated with the birds that regularly found their way under his netting and gorged themselves on his polyphemus caterpillars. The most abundant trees on his Massachusetts lot were oaks, so he thought a caterpillar that fed on oak foliage would be easier to breed. And so, Trouvelot decided to return to Europe where he could obtain different species, hopefully better suited to his needs.

It remains unclear whether Trouvelot actually brought gypsy moths back to America with him when he returned in March 1867, or if perhaps he ordered them from a supplier for delivery later. But regardless of how or precisely when they arrived, the gypsy moths were imported by Trouvelot and brought to his home on Myrtle Street. He began his new experiments in earnest, hoping he could cross the exotic gypsy moths with his silkworm moths and produce a hybrid, commercially viable species. Trouvelot was right about one thing – the birds didn't care for the hairy gypsy moth caterpillars, and would only eat them as a last resort. That would only complicate matters later.

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The First Great Gypsy Moth Infestation (1889)

Pre-1900 pesticide spray wagon.
Gypsy Moth Spray Rig (Pre-1900 _. From the archives of the USDA APHIS Pest Survey Detection and Exclusion Laboratory

The Gypsy Moths Make Their Escape

Decades later, residents of Myrtle Street told Massachusetts officials they remembered Trouvelot fretting over missing moth eggs. A story circulated that Trouvelot had stored his gypsy moth egg cases near a window, and that they had been blown outside by a gust of wind. Neighbors claim they saw him searching for the missing embryos, but that he was never able to find them. No proof exists that this version of events is true.

In 1895, Edward H. Forbush reported a more likely gypsy moth escape scenario. Forbush was a state ornithologist, and the field director tasked with destroying the now troublesome gypsy moths in Massachusetts. On April 27, 1895, the New York Daily Tribune reported his account:

A few days ago Professor Forbush, the ornithologist of the State Board, heard what appears to be the authentic version of the story. It appears that Trouvelot had a number of the moths under a tent or netting, fastened to a tree, for cultivating purposes, and he believed that they were secure. In this supposition he erred, and the error is likely to cost Massachusetts more than $1,000,000 before it is rectified. One night, during a violent storm, the netting was torn from its fastenings, and the insects scattered on the ground and adjacent trees and shrubbery. This was in Medford, about twenty-three years ago.

It is most likely, of course, that the netting was simply insufficient to contain the ever-increasing population of gypsy moth caterpillars in Trouvelot's backyard. Anyone who has lived through a gypsy moth infestation can tell you these creatures come rappelling down from the treetops on silk threads, relying on the wind to disperse them. And if Trouvelot was already concerned with birds eating his caterpillars, it's clear that his netting wasn't intact. As his oak trees were defoliated, the gypsy moths found their way to new sources of food, property lines be darned.

Most accounts of the gypsy moth introduction suggest that Trouvelot understood the gravity of the situation, and even attempted to report what had happened to area entomologists. But it seems if he did, they weren't too concerned about a few loose caterpillars from Europe. No action was taken to eradicate them at the time.

The First Great Gypsy Moth Infestation (1889)

Soon after the gypsy moths escaped his Medford insectary, Leopold Trouvelot moved to Cambridge. For two decades, the gypsy moths went largely unnoticed by Trouvelot's former neighbors. William Taylor, who had heard of Trouvelot's experiments but didn't think much of them, now occupied the house at 27 Myrtle Street.

In the early 1880's, Medford residents started finding caterpillars in unusual and unsettling numbers around their homes. William Taylor was collecting caterpillars by the quart, to no avail. Each year, the caterpillar problem worsened. Trees were completely stripped of their foliage, and caterpillars covered every surface.

In 1889, it seemed the caterpillars had taken control of Medford and the surrounding towns. Something had to be done. In 1894, the Boston Post interviewed Medford residents about their nightmarish experience living with gypsy moths in 1889. Mr. J. P. Dill described the infestation:

I do not exaggerate when I say that there was not a place on the outside of the house where you could put your hand without touching caterpillars. They crawled all over the roof and upon the fence and plank walks. We crushed them under foot on the walks. We went as little as possible out of the side door, which was on the side of the house next to the apple trees, because the caterpillars clustered so thickly on that side of the house. The front door was not quite so bad. We always tapped the screen doors when we opened them, and the monstrous great creatures would fall down, but in a minute or two would crawl up the wide of the house again. When the caterpillars were the thickest on the trees we could plainly here the noise of their nibbling at night, when all was still. It sounded like pattering of very fine raindrops. If we walked under the trees we got nothing less than a shower bath of caterpillars.  

Such public outcry spurred the Massachusetts Legislature to act in 1890, when they appointed a commission to rid the state of this exotic, invasive pest. But when has a commission ever proven an effective means to solve such a problem? The commission proved so inept at getting anything done, the Governor soon disbanded it and wisely established a committee of professionals from the State Board of Agriculture to exterminate the gypsy moths.

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What Became of Trouvelot and His Gypsy Moths?

Trouvelot's legacy.
Trouvelot's legacy. Gypsy moths continue to thrive and spread in the U.S. © Debbie Hadley, WILD Jersey

 What Became of the Gypsy Moths?

If you are asking that question, you don't live in the Northeastern U.S.! The gypsy moth has continued to spread at a rate of approximately 21 kilometers per year since Trouvelot introduced it nearly 150 years ago. Gypsy moths are well established in New England and the Mid-Atlantic regions, and are slowly creeping their way into the Great Lakes, the Midwest, and the South. Isolated populations of gypsy moths have been discovered in other areas of the U.S. as well. It is unlikely that we will ever completely eradicate the gypsy moth from North America, but vigilant monitoring and pesticide applications during high infestation years has helped slow and contain its spread.

What Became of Etienne Leopold Trouvelot?

Leopold Trouvelot proved much better at astronomy than he was at entomology. In 1872, he was hired by Harvard College, largely on the strength of his astronomical drawings. He moved to Cambridge and spent 10 years producing illustrations for the Harvard College Observatory. He is also credited with discovering a solar phenomenon known as "veiled spots."

Despite his success as an astronomer and illustrator at Harvard, Trouvelot returned to his native France in 1882, where it is believed he lived until his death in 1895.  


  • Napoleon III, Accessed online March 2, 2015.
  • "Massachusetts, State Census, 1865," index and images, FamilySearch, accessed 6 March 2015), Middlesex > Medford > image 41 of 65; State Archives, Boston.
  • "The American Silkworm," Leopold Trouvelot, American Naturalist, Vol. 1, 1867.
  • Reports of Observations and Experiments in the Practical Work of the Division, Issues 26-33, U.S. Department of Agriculture, Division of Entomology.  Charles Valentine Riley, 1892. Accessed via Google Books on March 2, 2015.
  • 1870 United States Federal Census [database on-line]. Provo, UT, USA: Operations, Inc., 2009. Images reproduced by FamilySearch.
  • The Great Gypsy Moth War: The History of the First Campaign in Massachusetts to Eradicate the Gypsy Moth, 1890-1901, by Robert J. Spear, University of Massachusetts Press, 2005.
  • "How the Gypsy Moth Got Loose," New York Daily Tribune, April 27, 1895. Accessed via on March 2, 2015.
  • "The Gypsy Moth Campaign," Boston Post, March 25, 1894. Accessed via on March 2, 2015.
  • Maps of Gypsy Moth, Lymantria dispar, Pest Tracker website, National Agricultural Pest Information System. Accessed online March 2, 2015.
  • Trouvelot: From Moths to Mars, New York Public Library Online Exhibition Archive, by Jan K. Herman and Brenda G. Corbin, U.S. Naval Observatory. Accessed online March 2, 2015.
  • E. Leopold Trouvelot, Perpetrator of Our Problem, Gypsy Moth in North America, US Forest Service website. Accessed online March 2, 2015.
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Hadley, Debbie. "How the Gypsy Moth Came to America." ThoughtCo, Apr. 5, 2023, Hadley, Debbie. (2023, April 5). How the Gypsy Moth Came to America. Retrieved from Hadley, Debbie. "How the Gypsy Moth Came to America." ThoughtCo. (accessed June 7, 2023).