Lymantria dispar dispar
Lymantria dispar dispar, commonly known as the gypsy moth, European gypsy moth, LDD moth, or North American gypsy moth or spongy moth, is a species of moth in the family Erebidae. It has a native range that extends over Europe and parts of Africa, and is an invasive species in North America.
Its larvae are polyphagous, consuming the leaves of over 500 species of trees, shrubs and plants. In its invasive range it is classified as a pest, notably one of the most destructive pests of hardwood trees in the Eastern United States. It is listed as one of the 100 most destructive invasive species worldwide.
Taxonomy
first described the species as Phalaena dispar in 1758. The subject of classification has changed throughout the years, resulting in confusion surrounding the species' taxonomy. This caused many references to describe this one species in different ways. The family has jumped between Lymantriidae, Noctuidae and Erebidae. L. d. dispar is designated the nominate subspecies of L. dispar.The species L. dispar has been split into several subspecies, including L. d. subsp. asiatica and L. d. subsp. japonica. The family is Erebidae, subfamily Lymantriinae. Lymantriid larvae are commonly called tussock moths because of the tufts of hair on the larvae.
Etymology
The name Lymantria dispar is composed of two Latin-derived words. Lymantria means "destroyer". The word dispar is derived from the Latin for "unequal" and it depicts the differing characteristics between the sexes.''L. d. dispar'' versus ''L. dispar'' usage
For the purposes of taxonomy, the common names European gypsy moth and North American gypsy moth represent the same subspecies, L. d. dispar, as opposed to subspecies of L. dispar from Asia.Confusion over the species and subspecies is widespread. For regulatory purposes, the U. S. Department of Agriculture has defined Asian Gypsy Moth as "any biotype of Lymantria dispar possessing female flight capability". despite Lymantria dispar asiatica not being the only classified subspecies that is capable of flight; even females of L. d. dispar can fly, if only very weakly. Traditionally, all L. dispar have been referred to as gypsy moth, including when referring to Japanese, Indian, and Asiatic subspecies.
Common name
In the species' native area, the English common name is "gypsy moth". In North America in July 2021, the Entomological Society of America announced it was delisting the common name gypsy moth as part of an effort to replace racist or otherwise offensive names, as Gypsy is considered an offensive slur by some in the North American Romani community. This led the Society to select a replacement name through a consultative process. In January 2022, they proposed the name spongy moth, in reference to the spongy mass of the egg casing. This new common name was formally adopted in North America in March 2022.Range
L. d. dispar is indigenous to Europe. In southeastern England, it was widespread in the 19th century, but became extinct except for occasional migrants soon after 1900. It then recolonised naturally from the 1990s; colonies were found in London from 1995 and Buckinghamshire from 2005, and more widely since.Introduction to North America
Lymantria dispar dispar was first brought to North America in 1869 and rapidly became an invasive species. Étienne Léopold Trouvelot imported the moths with the intent of interbreeding them with silk moths in order to establish a new silkworm industry in the West. The moths were accidentally released from his residence in Medford, Massachusetts. There are conflicting reports on the resulting actions. One states that despite issuing oral and written warnings of possible consequences, no officials were willing to assist in searching out and destroying the moths. The other notes that Trouvelot was, in fact, well aware of the risk and there is no direct evidence that he contacted any government officials about the moths' release. Though the Asiatic and the Eurasian moths were not classified as different subspecies in the 1980s, the differences were already notable.As noted in The Gypsy Moth by Forbush and Fernald, the moth was considered a nuisance just ten years after their release. The first major outbreak occurred in 1889, and Forbush and Fernald recount the extent of devastation: all the trees being defoliated and caterpillars covering houses and sidewalks and raining down upon residents. At first it was uncertain what species was responsible for the outbreak, but after the caterpillar was identified by entomologist Maria Elizabeth Fernald, an eradication program began in 1890. Eventually they would reach the Pacific Northwest, sporadically invading but so far not becoming established there, due to successful eradication campaigns.
Spread
The small larvae of the moth take to the air and are carried by the wind. The larvae spin silken threads and hang from them, waiting for the wind to blow. The light larvae have long hairs that increase their surface area, which are suitable for being carried aloft. The natural spread is slow, but transportation of the moth has led to isolated populations, with accidental transport of the eggs being noted. According to the United States Department of Agriculture, without intervention, this pest spreads about per year. A study published in 2012 suggests that storms can accelerate the spread, hypothesizing that strong easterly winds carried larvae across Lake Michigan to Wisconsin, a distance of at least.Firewood transport is a common way for the eggs to spread, since the moths will lay their eggs on dead wood. Attempts have been made to limit the movement of firewood to reduce the moth's spread.
Life cycle
Eggs
masses are typically laid on branches and trunks of trees, but may be found in any sheltered location, including rocks, foliage and vehicles. Females are flightless, so they lay eggs on a surface near where they emerged from their pupa. The eggs are covered in a coating of hairs. The covering provides protection from predators and parasites, and may be important for insulating the eggs from cold and for sealing in moisture.The larva inside the egg becomes fully developed in about one month after being laid and then enters diapause to overwinter. The egg is in the overwintering stage lasting for eight or nine months. Development ceases in preparation for the winter. After an acclimation stage, during which the larva inside the egg reduces its water content, eggs can withstand freezing temperatures. The larva inside the egg resumes activity in the spring, and reabsorbs water. The larva will then chew through the chorion of the egg and the protective hair of the egg cluster in the spring.
Egg clusters are usually an oval about wide and long. The egg masses are buff yellow-brown, likened to a manila folder, but may bleach out over the winter months. As the female lays them, she covers them with hair-like setae from her abdomen. Egg clusters contain from 100 to 1000 eggs. Due to the appearance of the eggs, several common names have emerged; the German Schwammspinner and French la spongieuse refer to the spongy texture of the egg cluster.
Larvae
Larvae emerge from egg masses in the spring. Most larvae hatch within a week, but can take as long as a month. The new larvae remain on or near the egg cluster if they hatch in rainy weather or if the temperature is below. The larvae will disperse even if there is enough foliage for growth, hanging from silk threads and waiting for the wind to send them aloft. The larvae are about long when they first hatch and will grow to.The larva will first feed on the leaf hairs and then move onto the leaf epidermis. Feeding occurs in the daytime, primarily in the morning and late afternoon. As the larva grow, the feeding becomes a nocturnal activity. When not eating, the larva will remain on the underside of the leaf and make a mat of silk for attachment.
To grow, the larva must molt. Larvae are characterized by the term instar, which refers to the number of times a larva has molted; a first-instar larva has not yet molted, a second instar has molted once, a third instar twice, etc. Males typically are five instars and females are six instars. When the larvae reach the fourth instar, they become nocturnal feeders, and will return to their resting places at dawn, hiding under flaps of bark, in crevices, or under branches - any place that provides protection.
Newly hatched larvae are black with long, hair-like setae. Older larvae have five pairs of raised blue spots and six pairs of raised brick-red spots along their backs, and a sprinkling of setae. As the larval stage comes to an end they cease feeding and surround themselves in a silken net.
Distinguishing the larvae from other species
Larvae can be distinguished from other species of caterpillar by its spots. Close to the head, five pairs of blue spots and six pairs of red spots towards its tail. This distinction will prevent confusion with the spiny elm caterpillar and other caterpillars. Eastern tent caterpillars can be distinguished by their silky tents in trees, the presence of a back stripe, and their preference for cherry trees.Pupae
The larvae reach maturity between mid-June and early July, then enter the pupal stage, during which larvae change into adult moths. Pupation lasts from 14–17 days. The adult moth will emerge, fully developed, by splitting the pupal skin.When the population is spread out and running low, pupation can take place under flaps of bark, in crevices, under branches, on the ground, and in other places where larvae rested. During periods when population numbers are dense, pupation is not restricted to these locations, but can take place in sheltered and open locations, even exposed on the trunks of trees or on foliage of nonhost trees. Usually, the caterpillars create flimsy cocoons made of silk strands holding the leaf together, while others do not cover their pupae in cocoons, but rather hang from a twig or tree bark, like butterfly pupae do.