If you aren’t an entomologist, there are probably few insect varieties that you know by species name. But most, if not all, citizens of Massachusetts and her surrounding states know the gypsy moth. Known by the Latin name
Lymantria dispar, this particular moth has been devastating woodlands and forests in Massachusetts for over a century.
The moth was accidentally introduced to Massachusetts in 1869, when a French-born amateur entomologist named Étienne Léopold Trouvelot imported the insect, probably via egg masses, to his home in Medford, Mass. He was occupied with experiments involving silk worms and he hypothesized that breeding silk worms with the robust gypsy moth found in Europe would allow the resultant cross breed to better survive handling and relocation as well as have a more varied diet and avoid existing natural predators, all of which made it ideal for commercial production of silk.
At the time, entomology was still a growing and disorganized science and the importation of insect species was not considered as potentially harmful or invasive. These “men of science were slow to understand the adverse consequences, and government authorities were ambivalent about regulating the practice… there were no legal, moral, or ethical restraints against the practice of transporting alien insects anywhere” Robert J. Spear wrote in his book
The Great Gypsy Moth War (2005). Further, Trouvelot’s friend remembered that the backyard enclosure that he used to breed moths was enclosed by netting with significant holes, often large enough for native birds to get in and eat the experimental larvae. Despite these recollections, today we have no evidence of how the first eggs, larvae, caterpillars or adult gypsy moths escaped the enclosure.
Trouvelot eventually turned his attention to other projects and experiments and the moth did not appear to trouble many people for several decades. Later in the 1890’s some witnesses and neighbors remembered Trouvelot searching for the insects, even destroying egg clusters and notifying local authorities of the insect’s escape. However, there is no evidence of these warnings, and by the time the gypsy moth became a problem in the 1890s, Trouvelot had long since moved back to France.
In 1889, swarms of gypsy moths invaded Medford. “Citizens could only stare in disbelief as the dirt streets became carpeted with millions of larvae that seemed to have materialized out of the earth… Great pulsating masses of larvae stripped any plant along their path in minutes,” (Spear). The train rails running through Medford were stained green by crushed larvae, and as they swarmed homes the sound of the larvae eating any and all vegetable matter both inside and outside homes was audible (Spear). The town roads commission attempted to battle the insects, but eventually the fear that the insect would attack agricultural communities inspired ambitious entomologists to urge Medford selectmen to petition the Legislature for assistance.
The outbreak had inspired the organization of the American Association of Official Economic Entomologists, later simply the Association of Economic Entomologists. Economic Entomologists believed that the insect had to be fully exterminated, rather than suppressed and controlled, to protect agricultural interests and with their urging the State Legislature passed an act that more or less declared war on the invasive species in 1890.
The Commission, under the Board of Agriculture, organized an army to exterminate the insect. By then the gypsy moth was spreading, found in the surrounding towns of Malden, Melrose, Stoneham, and more. The bulk of the army was made up of “privates” who were trained to spray Paris green, an arsenic-based insecticide. Spraying was expensive, and other crews instead scrapped egg masses away, wrapped trees with burlap to stop caterpillars from climbing to the foliage, or burned trees and brush altogether to kill off potential feeding grounds. Only after years of using arsenic-based insecticide would entomologists discover that gypsy moths are impervious to this particular chemical and that spraying arsenic had actually damaged native populations of birds and insects that might have fed on the gypsy moth.
The Gypsy Moth Commission was dependent on yearly appropriations from the Legislature, which made it difficult to hold on to trained personnel when funds ran out for a particular year. They also encountered resistance from private citizens who disapproved of the Commission’s employees coming onto their land without their permission, and much of the testimony provided in hearings regarding the gypsy moth war was given from these individuals. When the infestation threatened Middlesex Fells, the new Metropolitan Park Commission also stood in opposition to any destruction of public woodlands.
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| A page of testimony from the 1896 hearings |
Despite years of work and reports swearing that the Commission was curbing the infestation, the moth continued to gain ground through Massachusetts to the utter bafflement of the economic entomologists involved in the Gypsy Moth Commission. They began to doubt that extermination was even possible. By 1900, an investigative committee began looking into the Gypsy Moth Commission and hearings were held to question those involved. The resultant report found that the efforts were misdirected and the expenditure of state funds had been “extravagant” due to mismanagement. The Commission did not remain for much longer.
The gypsy moth infestation continued to spread and by 1922 they were found in every single town and city in Massachusetts. The federal government eventually got involved as the infestation crossed state lines, and with the invention of DDT (a synthetic chemical compound) in 1946 aerial spraying began on infested areas. However, that didn’t stop the infestation of 1981, which is believed to be “the nadir of the struggle against the gypsy moth, a time when the insect seemed unstoppable and when its voracious habits results in the ‘defoliation’ of thirteen million acres--the greatest damage to trees ever caused by a single insect species in the United States” (Spear). Today, the state’s management has shifted from spraying to relying on nature to manage gypsy moth populations, including a fungus known as Entomophaga maimaiga that spreads quickly and causes significant gypsy moth mortality (Gypsy Moth in Massachusetts). Even so, the insect continues to be an issue both in the state of Massachusetts and throughout the United States.
Further reading:
Alexandra Bernson
Reference Staff
