# Lymantria dispar

Lymantria dispar, also known as the gypsy moth or the spongy moth, is a species of moth in the family Erebidae native to Europe and Asia. Lymantria dispar is subdivided into several subspecies, with subspecies such as L. d. dispar and L. d. japonica being clearly identifiable without ambiguity. Lymantria dispar has been introduced to several continents and is now additionally found as an invasive species in Africa, North America and South America. The polyphagous larvae live on a variety of deciduous and coniferous trees and can cause severe damage in years of mass reproduction. Due to these features, Lymantria dispar is listed among the world's 100 worst invasive alien species.

## Etymology

The etymology of "gypsy moth" is not conclusively known; however, the term is known to have been in use (as 'Gipsey') as early as 1832.
Moths of the subfamily Lymantriinae are commonly called tussock moths due to the tussock-like tufts of hair on the caterpillars.$^{:9}$
The name Lymantria dispar is composed of two Latin-derived words. The generic name Lymantria means 'destroyer'. The species epithet dispar means 'to separate' in Latin; it refers to the sexual dimorphism observed in the male and female imagines.$^{:9}$
In July 2021 the Entomological Society of America decided to remove the name "gypsy moth" from its Common Names of Insects and Related Organisms List as "hurtful to the Romani people", since gypsy is considered an ethnic slur by some Romany people in North America. In January 2022, the new common name "spongy moth" was proposed, as a translation from the French name "spongieuse" for the species, referring to the sponge-like egg masses laid by L. dispar. Since the name Gypsy is widely embraced by Roma people as a self-referenced demonym in Europe, there has been no similar call to change the insect's name in its native area.

## Taxonomy

The European native, and introduced North American, Lymantria dispar moths are considered to be the same subspecies, Lymantria dispar dispar.$^{:6}$ Confusion over the classification of species and subspecies exists. The U. S. Department of Agriculture defines the Asian subspecies as "any biotype of L. dispar possessing female flight capability",$^{:5}$ despite L. d. asiatica not being the only accepted subspecies that is capable of flight.$^{:6}$ Traditionally, L. dispar has been referred to as "gypsy moth" even when referring to Japanese, Indian and Asiatic populations.$^{:5}$

### Subspecies

| Subspecies | Distribution | Identifying characteristics |
| Lymantria dispar dispar | Europe, western Asia and north Africa,$^{:6}$ introduced to Eastern North America | Females winged but flightless$^{:6}$ |
| Lymantria dispar asiatica | Eastern Asia,$^{:6}$ introduced to western North America and to Europe | Females winged and capable of flight; attracted to lights$^{:6}$ |
| Lymantria dispar japonica | All of Japan$^{:6}$ | Large males, very dark brown$^{:6}$ |
The European subspecies (Lymantria dispar dispar) is native to temperate forests in western Europe. It had been introduced to the United States in 1869, and to Canada in 1912.
The Asian subspecies (Lymantria dispar asiatica) is native to temperate Asia east of the Ural mountains. Since the early 1990s it has also been detected along the West Coast of temperate North America. From Southern Europe it is spreading northwards into Germany and other countries, where it hybridizes with the European subspecies, L. d. dispar. A colony had been reported from Great Britain in 1995.

## Biological pest control measures

Lymantria dispar was accidentally introduced into North America by artist and astronomer Étienne Léopold Trouvelot in 1869, who imported it from Europe while looking for a source of silk to replace the shortage of cotton caused by the American Civil War. Afterwards, several species of parasitoids and predators have been introduced as biological control agents in attempts to help control this moth. Beginning in the late 1800s, at least ten species were established this way, but for nearly a century, there was little regulation or research on the effectiveness or non-target effects of these introduced natural enemies. Several were generalists that offered little control of L. dispar and attacked other native insects. One such species is the tachinid fly Compsilura concinnata, which attacked many other host species (over 180 known hosts documented), decimating many of the large moth species previously abundant in the Northeast. Another is the encyrtid wasp Ooencyrtus kuvanae which attacks L. dispar eggs but is not strictly host specific, and also parasitizes the eggs of other Lepidoptera species. The most effective control agents are microbial pathogens: a virus (LdmNPV), and a fungus (Entomophaga maimaiga).

### Current status in the USA

In June 2024, the severity of the outbreak in the Northeast and Midwest of the United States was reported by Scientific American. Some places in these regions were experiencing one of the most severe outbreaks ever recorded, with some areas reporting densities exceeding 2,500,000 caterpillars per hectare (1,000,000 per acre), and certain regions have been grappling with this issue for five consecutive years.
Since the introduction of the species to North America, L. dispar has caused significant ecological damage. Over the past century, its range has expanded at an average rate of 21 km (13 mi) per year, resulting in the cumulative defoliation of 33,000,000 ha (82,000,000 acres) of forest between 1970 and 2013. The U.S. Forest Service allocates an average annual budget of $30 million toward control efforts. However, climate change has contributed to the prolongation of outbreak cycles, which typically occur every eight to twelve years. This has led to a more frequent and severe impact on the environment.
Defoliation by L. dispar triggers chemical defenses in quaking aspen, rendering them unfit host trees for Polyphemus moths, posing an additional threat to their conservation.