How one man ruined America* and left us with millions of worms in his wake

Well, hello there!
*Or at least part of America, including Michigan.


By Victoria Mullen



The gypsy moth has been the bane of the northeastern and Midwestern U.S. (and Canada) for nigh on over a century now.


Originally introduced to the U.S. as a possible alternative to the finicky silkworm (which favors only mulberry leaves), the hardy gypsy moth has a voracious appetite for oak trees as well as several species of trees of shrubs, including (in alphabetical order): apple, aspen, basswood, birch, hawthorns, poplar, speckled alder (not to be confused with pickled herring), sweet gum and willow, to name a few. Older larvae feed on Atlantic white cypress, cottonwood, hemlock, pine and spruce. All told, these things will eat more than 300 different species of trees.


Before getting too far into the meat of the matter — which is, admittedly, overwhelming — there are some things we can do, and I won’t leave you high and dry. You’ll find tips at the end of this essay.


A single gypsy moth caterpillar can consume 11 square feet of vegetation during its lifetime; the presence of millions of caterpillars can defoliate 13 million acres of trees in the United States in just one season.


Normally, nature’s creatures keep each other in check. So, what accounts for the millions of trees that are decimated each year by gypsy moth larvae? As with most unnatural disasters, this one arose out of human greed and error — a failed attempt to cultivate a silk industry in America. We should know better.


Here, then, is the sordid tale of an enterprise gone very, very wrong.


The man also had a beard

Picture, if you will, a Frenchman in the mid-1800s.

A man with a moustache. A man with an entrepreneurial spirit. A man who saw an opportunity and without an iota of thought for the future, just went for it.


That man was Étienne Léopold Trouvelot, an artist and astronomer who showed real talent in those fields. Some examples of his work are shown here (also scroll down).


Originally from Aisne, France, Trouvelot and his family were forced to flee Louis Napoleon’s coup d’état in 1852. They settled in Medford, Massachusetts at 27 Myrtle St., where our proud, little breadwinner supported himself and his family as an artist and astronomer, painting lovely pictures of the planets as he saw them. We can only assume his renderings were the result of a creative eye and not mind-altering substances.


Jupiter as Étienne Léopold Trouvelot saw it. Trouvelot was an artist and astronomer who should have stuck to sketching and star gazing

A pause here to reflect: I personally know dozens of artists would would kill to have the opportunity to make a living with their art. But it just wasn’t enough for Trouvelot.


No, sirree.


Indeed, one day, during one of his random, no doubt fitful, musings, the Frenchman decided, “Eureka! I shall study Entomology!” (from Greek ἔντομον, entomon “insect”; and -λογία, -logia)—the scientific study of insects, a branch of zoology.


Only he likely decided this in French.


And on that fateful day, life as all future inhabitants of the northeastern and Midwestern US of A would come to know it, was forever altered.


Planet Mars by Trouvelot

Actually, this should come as no surprise. Trouvelot’s interest coincided with a nineteenth-century fad—raising silkworms to become rich beyond belief. After all, silk had been a symbol of great wealth for centuries.


Several kinds of wild silk, which are produced by caterpillars other than the mulberry silkworm, have been known and used in China, South Asia, and Europe since ancient times. First developed in ancient China, the earliest example of silk fabric dates from 3630 BC.


At its zenith, the silk trade reached as far as the Indian subcontinent, the Middle East, Europe and North Africa. So extensive was this trade that the major routes between Europe and Asia came to be known as the Silk Road.


Silk route

In ancient times, silk from China was an incredibly profitable and desirable luxury item. People from Persia and many other civilizations benefited mightily from its trade.


Fast-forward to the mid-1860s, in Medford, Massachusetts…

…where our anti-hero, Trouvelot, had became utterly fixated on the biology and culture of worms — silkworms, specifically — because what man in his right mind would ignore an opportunity to become richer than his wildest dreams?


To his credit, Trouvelot was meticulous with his research comparing the qualities of silk produced by a variety of native North American silkworms. After a time, he  concluded that Antheraea Polyphemus (NOT a gypsy moth) showed the greatest possibilities for commercial silk production. This species occurs throughout the United States and southern Canada, feeds on several hardwood species, and is reported to produce a very high-quality silk.


Courtesy of Purdue University
All fine and dandy. But our guy was obsessed. For eight years, from 1860 until at least 1868, Trouvelot developed techniques for mass rearing A. Polyphemus. Seriously, I can think of so many other, vastly more interesting things to pursue for one year, let alone eight.


Experiments rearing larvae on cut foliage were “meh” at best; these things preferred living saplings. At the peak of his operation, our guy had more than a million larvae under culture in a five-acre wooded area behind his house. I can’t begin to imagine how he managed to cover the entire area with nets, but that he did, to discourage birds from feeding upon his little darlings.


“The first year I found only two caterpillars.”


Not content to limit his experiments to species native to North America, in the late 1860s, Trouvelot brought home a shipment of live gypsy moth eggs upon his return from a trip to Europe. His plan was to crossbreed gypsy moths with a silk-producing North American species to develop a strain resistant to the protozoan disease, Nosema bombycis, which had decimated the silk industry in much of Europe.


He soon learned that the species were incompatible for breeding. Nonetheless, he kept a few gypsy moths in a room in his house. As souvenirs, perhaps?


Who can say?


And he continued researching. He fed his caterpillars. He nurtured them. He raised them as his very own. And he watched in awe as they cycled through the egg/larvae/pupae/moth stages. These little buggers ate anything. And, they produced silk, dammit!


Then, Mr. Trouvelot had the unmitigated gall to write about it.


gypsy moth
Female on the prowl

“In 1860, after having tested the qualities of the cocoons of the different species of the American silk worms,” he wrote, “I endeavored to accumulate a large number of the cocoons of the Polyphemus moth, for the future propagation of this species. At first the undertaking seemed very simple; but who will ever know the difficulties, the hardships and discouragements which I encountered.”


Poor Trouvelot! One could almost feel sorry for him. The first year, he found just two insects, one half dead and the other still in its cocoon, refusing to emerge.


“Imagine my anxiety; it was a year lost,” lamented Trouvelot in his journal.


Indeed. But our anti-hero was tenacious if nothing else, and he wasn’t about to let the little matter of the absence of insects to derail his mission. And so, the second year, he found a dozen worms and studied them further to learn more about their habits. His patience was rewarded.


“It is astonishing how rapidly the larva grows, and one who has no experience in the matter could hardly believe what an amount of food is devoured by these little creatures.”


“A pair of these insects came out of the cocoon at the proper time, and I obtained from their union three hundred fecundated eggs,” he crowed.

female gypsy moth
Female gypsy moth


This went on for a few more years, as our dear Frenchman became expert in cultivating his little pretties. He describes his efforts in detail in his treatise, The American Silk Worm.


About the gypsy moth, he made this astute observation:


“What a destruction of leaves this single species of insect could make if only a one-hundredth part of the eggs laid came to maturity! A few years would be sufficient for the propagation of a number large enough to devour all the leaves of our forests.”




As Murphy’s Law is wont to dictate, in 1868 or 1869, several of Trouvelot’s gypsy moths — not content within the confines of four walls and probably feeling neglected (really, who could blame them?) — escaped the room in which he kept them. It is written that he was quite upset about the incident and it is thought that he “publicly” announced it, having become “all too aware” of the danger of a species like this run amok.

Gypsy moth pupae (ugh… I can’t even…)


Soon after his experiment, Trouvelot gave up on the worms, returned to art and astronomy and by 1882, had gone back to France. Shortly thereafter, his old neighborhood suffered an enormous gypsy moth infestation. Residents were at first intrigued, but that was short-lived.


And just as Mr. Trouvelot had postulated, the gypsy moth became one of the most destructive pests of trees and shrubs to ever be introduced into the United States. Since 1970, gypsy moths have defoliated more than 75 million acres in the United States.


So, here we are, more than 100 years later, still dealing with this foppish mess.

It’s now up to us to help prevent the further spread of this destructive pest, and this includes inspecting and removing gypsy moth egg masses from household goods before moving from an infested to a non-infested area.


Caterpillars on the side of a shed
Frass (i.e., caterpillar poop) on a picnic table
Caterpillars on a garden gnome
These creatures have absolutely no redeeming qualities, especially at the pupae stage.


And these things are everywhere, from the undercarriages of campers and cars to mailboxes, to the siding of houses and the surfaces of rocks. Even innocent garden gnomes and picnic tables. You name it, and they are likely to be there.


On the plus side, they’re not fond of American holly, American sycamore, ash trees, balsam fir, black walnut, butternut, catalpa, cedar, cucumber trees, flowering dogwood, mountain laurel, rhododendron shrubs and tulip-trees, so be sure to plant plenty of these, BUT the worms will make an exception when densities are very high.


Is all hope lost? Well, maybe a goodly portion of hope is forever gone, but I offer you here, at no extra charge, a handy-dandy little guide:


Tan, fuzzy-wuzzy egg mass
Gypsy Moths, in a nutshell

Gypsy Moth (Lymantria dispar)

Established in Michigan (unfortunately)


First, is it a Gypsy moth? These are the telltale signs:

  • The nasty little caterpillars emerge from tan, fuzzy egg masses in April and feed on leaves through late June
  • Caterpillars are hairy, with a yellow and black head and 5 pairs of blue spots, followed by 6 pairs of red spots. They fancy themselves fashionable; they are not.
  • Mature caterpillars are 1.5 to 2 inches in length. They start out tiny and molt several times. Each time they molt, their appetite increases exponentially.
  • Leaf debris and small, round frass (i.e., insect larvae excrement) found under trees are indications of gypsy moth infestation. Apparently the mention of “excrement” is off-putting to civilians, so “frass” it is.
  • Male moths’ wings have a wavy pattern of brown to dark brown and span 1.5 inches.
  • Female moths are larger than males and do not fly. Wings are white to cream with wavy black markings
  • These guys do not pitch tents. Thank goodness for small favors. That is the domain of the tent caterpillar, an altogether different pest.
gypsy moth (2)
A gypsy moth caterpillar who fancies himself fashionable



  • Gypsy moths most often feed on the leaves of oak and aspen but can also be found on hundreds of other plant species.


Native Range:

  • Europe and Asia


U.S. Distribution:

  • Northeastern U.S. west to Minnesota


Local Concern:

  • Gypsy moth caterpillars defoliate trees, leaving trees vulnerable to diseases and other pests, which may lead to tree mortality.
  • During large outbreaks, debris and frass (again, excrement) from feeding caterpillars can be disruptive to outdoor activities. Those strange messes you’ve seen on picnic tables and had no clue as to what they were? Now you know.


Hitching a ride in an undercarriage of a vehicle
Pathways of Spread:

  • Though female moths do not fly, small caterpillars can be blown by the wind to other trees.
  • Gypsy moth egg masses and pupae can be unknowingly transported on firewood, vehicles and recreational gear.


Short distance dispersal of this species happens by way of “ballooning”—where caterpillars are windblown and dispersed (think: hot air ballooning). Humans unwittingly transport egg-laden materials as females will lay their egg masses anywhere, including on man-made objects such as vehicles.


The City of Wyoming is doing something about it. Get involved!

The city is surveying neighborhoods for the presence of gypsy moths and their larva. Formal gypsy moth assessments take place in the fall to determine if the following spring will provide the best opportunity for treatment. Go here to learn about Wyoming’s suppression efforts and to complete a survey — the city wants to know where you see ’em. Plus, here’s a map where suppression efforts are in progress. More info here, too.


Check under your eaves
There are several techniques you can use to help suppress this pest. Below are some articles that will help you understand the gypsy moth, its treatment and what we can use to minimize this pest on our property.


Direct any questions about the City of Wyoming Gypsy moth Suppression Program to Kelli VandenBerg at 616.530.7296.


As of May 26, The City of Wyoming concluded its 2016 aerial spraying to suppress Gypsy Moth Larvae in selected areas.