LYMANTRIA DISPAR: CHARACTERISTICS, HABITAT, LIFE CYCLE, FEEDING - BIOLOGY - 2025

Lymantria dispar is a lepidopteran insect belonging to the Erebidae family. It has two subspecies: Lymantria dispar dispar (European and North American) and Lymantria dispar Asia. The most striking difference between both subspecies is that females of the Asian variety can fly.

This insect is widely distributed throughout the world geography, although it naturally belongs to Asia, a large part of Europe and a small part of Africa. However, thanks to human action, it was introduced to the American continent, where it has become a veritable plague.

Lymantria dispar. Source: Muséum de Toulouse

In the American continent Lymandria dispar has become a serious problem, since the rapidity with which it has spread and conquered new territories has negatively affected forests, causing the loss of leaves on the trees in which it grows.

In the regions of which it is indigenous, this type of problem does not arise, since there are natural biological mechanisms that control its population.

General characteristics

-Species: Lymantria dispar.

Morphology

Lymantria dispar is a species in which a marked sexual dimorphism is observed in its adult individuals. This means that there are differences between females and males.

The first difference between the two is the size. The male has a wingspan of approximately 50 mm, while that of the females can reach and exceed 60 mm.

Lymantria dispar. Male specimen. Source: Muséum de Toulouse

Males have a light brown body, while their wings are darker brown. Likewise, there are black lines throughout the length of its wings. In addition, their antennae have a feathery appearance and texture.

In the case of female specimens, both the body and the wings are, for the most part, white. In addition to this, its body is covered by a fine layer of hair. Their antennae are different from those of males, as they have a threadlike appearance.

Lymantria dispar. Female exemplar. Source: Muséum de Toulouse

In the case of the larvae, they are black and very hairy, where there is also no difference between females and males. Larvae that have fully developed have blue (five pairs) and red (six pairs) spots on their dorsal surface.

Habitat and distribution

Lymantria dispar is a species of insect that is native to Asia, Europe, and Africa. In Europe it is found mainly to the south, while in Africa it is located in some northern regions.

It is in Asia where it is most widespread, found in Central Asia, South Asia and Japan.

In these locations is where it is found naturally. However, it is possible to find it also in the American continent, specifically in the United States. This insect was accidentally introduced at the end of the 19th century in the Anglo-Saxon country and, from that moment, its expansion throughout the country has not stopped. Note that it is very common in the northeastern region of the United States.

However, the habitat in which these moths are found is characterized by being deciduous forests. This means that they are made up of trees that annually lose their leaves, thanks to the passage of the different rainy and drought seasons. They are generally found in forests with these characteristics that do not exceed 1200 meters in altitude.

Regarding the specific type of trees in which this type of insect is found, it can be said that it occupies large species such as poplar or willow. Specimens have also been identified in linden and trembling. There are few occasions on which this type of moth has been found in conifer-type trees.

Reproduction and life cycle

The type of reproduction these moths experience is sexual. Through this, the fusion of the female gametes (ovules) and the male gametes (sperm) is necessary. Only in this way are new individuals generated.

They present an internal fertilization, that is, the ovules are fertilized inside the female's body. However, before copulation occurs, it is imperative that the mating ritual take place.

Mating or courtship ritual

The mating ritual is very similar to that of many species in the animal kingdom. This consists of the release, by the female, of chemical substances known as pheromones.

Pheromones are synthesized by a gland that females possess and that are located near the edge of the abdomen. The main function of pheromones in any animal species is to attract individuals of the opposite sex, with the sole purpose of reproducing.

In the case of Lymantria dispar, the females release the pheromones as soon as they emerge as an adult insect from the pupae. These pheromones are so powerful that they can attract male individuals from a great distance.

In addition to this, to release the pheromone, the female performs a characteristic movement, referred to by specialists as "call".

Copulation and fertilization

Once the male is attracted to the pheromones and meets the female, a copulation process occurs that is quite straightforward. The female simply raises one of her wings to facilitate access to the male and thus be able to couple their bodies.

Fertilization occurs by transfer of spermatophore. This is a structure within which are all the sperm that the male produces at any given time.

Importantly, a male moth can mate with multiple females. Opposed to this, in general, females can only mate with a male, since at the end of copulation, they stop synthesizing pheromones.

Egg pose

After fertilization occurs, the female proceeds to lay the eggs. However, unlike what happens with other species of insects, Lymantria dispar does not arrange each egg individually, but instead places them in groups, known as clusters or masses.

Each egg mass is approximately 4 cm long. They are oval in shape and their color is yellowish brown. In addition to this, the female covers them with hair-like structures, in order to protect them from possible predators. Each egg mass can hold up to 1000 fertilized eggs.

The place that females choose to lay their eggs is often near the site where they pupated. This is so because females, despite having wings, do not have the ability to fly, so their movement is limited.

Generally the eggs are placed in the trunk of the trees, or in their branches. However, egg masses have also been observed in places such as under rocks or even inside inhabited houses.

Inside the egg, the development of the larva takes about a month. After that time has elapsed, the egg goes into hibernation. This can last up to 8 months. After the hibernation period, the larva reactivates and makes its way to the outside, eating the chorion of the egg and the protective layer of the egg mass.

Larvae

When the larvae emerge from the eggs, they are approximately 3mm long. They feed mainly on leaves. The feeding process occurs during the day, although as the larvae grows and develops, it becomes a nocturnal activity.

The way in which the larva grows is through molting. Some specialists call each larval stage a stage. Females typically have six larval stages, while males only have five.

From the fourth stage, the feeding habits of the larvae become nocturnal, so they spend the whole day in inactivity, hidden in protected places, from which they only come out to feed.

Lymantria dispar larva. Source: Patrick Reijnders

Likewise, the larvae have the ability to produce silk thanks to the glands they possess. In terms of appearance, the smallest larvae, which have just hatched from the eggs, are black and hairy.

As they move, they undergo certain changes. The larvae that are in their last larval stage present five pairs of blue spots and six pairs of red spots on their back.

The completion of the larval stage is determined by the cessation of feeding and the production of abundant quantities of silk, with which they are completely surrounded.

Pupa

The pupae are structures, within which the larvae undergo certain changes until they transform into an adult individual. Those of the females are larger than those of the males. They are dark reddish brown in color.

The duration of this stage of the cycle is variable between females and males. In the first, it lasts approximately 10 days, while in males it can last up to 13 days. After this time, the adult insect emerges, dividing the skin of the pupa.

Adult

The adult males emerge from the pupae several days before the females. There are marked morphological differences between the two, which have already been mentioned. Likewise, males tend to fly, while females, despite having large wings, do not have such capacity. It is worth noting that in the case of the Asian subspecies, the females can fly.

The adult insect has the sole purpose of reproducing, so from the moment it emerges from the pupa, the female begins to spread pheromones to attract males.

Feeding

Lymantria dispar is an organism considered heterotrophic, since it must feed on other living beings or on substances that they make. This is because they do not have the ability to synthesize their own nutrients.

In this sense, this insect is classified as herbivore, since it feeds solely and exclusively on plants. The feeding of the animal occurs mainly when they are in the larval stage.

The larvae can be very voracious, and can become a phytosanitary problem if the population is very abundant. The problem is that they are often responsible for the defoliation of the trees in which it is found.

The adults do not feed, due to an atrophy experienced by their spirits (tube used by Lepidoptera to suck nectar).

References

1. Brusca, RC & Brusca, GJ, (2005). Invertebrates, 2nd edition. McGraw-Hill-Interamericana, Madrid
2. Ministry of Environment. (1995) Lymantria dispar. Obtained from juntadeandalucia.es
3. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
4. De Liñán, C. (1998). Forest entomology. Ediciones Agrotécnicas SL Madrid
5. Hickman, CP, Roberts, LS, Larson, A., Ober, WC, & Garrison, C. (2001). Integrated principles of zoology (Vol. 15). McGraw-Hill.
6. Lymantria dispar. Retrieved from: iucngisd.org
7. Munson, S. (2016). Gypsy moth, Lymantria dispar. (Lepidoptera: Erebidae). Conference at International Congress of Entomology.
8. Wallace, S. (1999). Lymantria dispar Gypsy moth. Plant Health Survey Unit. Ottawa.