Stuffed caterpillar characteristics, habitat, reproduction, bite

Robert Johnston

The plush caterpillar (Megalopyge opercularis) is a poisonous moth that belongs to the Megalopygidae family. The larva of this species is covered with long setae, which resemble hairs. Among these bristles are spines, at the bases of which are the poison glands.

When the man's skin brushes against the caterpillar, the spines become embedded, thus injecting the toxic substance. The injury causes an extremely painful reaction, which, if not treated in time, could cause serious complications in the body.

Stuffed caterpillar. Source:

As for the adult moth, its body is covered with bristles. These vary in color, and can be from lemon yellow to opaque green. In relation to their legs, they are equally hairy, white in color and with a black end..

Megalopyge opercularis it is endemic to the southeastern United States, mainly in the states of Louisiana and Texas. However, cases of stuffed caterpillar bites have been reported in some South American countries, including Venezuela and Argentina..

Article index

  • 1 Features
    • 1.1 - Eggs
    • 1.2 - Larvae
    • 1.3 - Pupae
    • 1.4 - Adults
    • 1.5 - Predators
  • 2 Habitat and distribution
  • 3 Playback
    • 3.1 - Playback
    • 3.2 - Stages of development
  • 4 Food
  • 5 Sting and treatment
    • 5.1 Treatment
  • 6 References 


- Eggs

The eggs of the Megalopyge opercularis They have rounded ends and are approximately 1.2 millimeters long and 0.6 millimeters wide. In relation to its coloration, it is pale yellow.

- Larvae

In the larval stage, the number of stages is not precise, and can be variable according to the species. However, some experts presume that there must be between 5 and 6 stages, while others point out the existence of 8 to 10 stages of development. An adult larva can grow to around 4 centimeters long, including the tail..

During the first and second stages, the integument is yellow, but in later stages it turns white or light greenish. As the larvae molt, the number of mushrooms that covers it increases, which makes it hairier.

In all phases, the caterpillar has rows of warts, which have hollow spines. At the base of each of these structures there is a poison gland. These spines turn darker in the final stages.

Regarding the coloration, it can be from dark gray, golden brown to greyish white. Often has a bright orange stripe, extending lengthwise.


The larvae of the Megalopyge opercularis They have 7 pairs of false legs. In addition, the abdominal segments have postspiracular appendages. These are difficult to appreciate due to the thick layer of mushrooms that exists in that area..

Specialists have assigned a defensive function to these appendages. This is because its stimulation causes the larvae to move the warts with spines towards the spiracles..


The cocoons of the stuffed caterpillar can measure between 1.3 and 2 centimeters. On the back they have a small hump, while the flattened end is formed by an operculum.

In the case of newly spun cocoons, they have a thin front, which extends well beyond the operculum. As the cocoon ages, it wears out, so this front part collapses. Thus, a flattened silk pad is formed in front of the operculum.

- Pupae

The abdominal segments of the pupa are attached to the surface of the body. However, in this species, the fourth to the sixth segment are mobile.

- Adults

In the adult stage, the moth is small in size, the female being larger than the male. As for the wingspan, it measures 2.4 to 3.6 centimeters. Its body is covered with a thick layer of mushrooms, which on the thorax are orange..

The antennae of the stuffed caterpillar are comb-shaped, presenting branches or teeth on both sides. The male's antenna is thicker and wider than that of the female, which is thin and fine..

In relation to the wings, the hind wings have a creamy yellow hue. As for the front ones, they are yellow. On the upper edge it has a black line, which starts from the base, but does not reach the end of it. This stripe is much darker and more pronounced in males..

In addition, in the basal 2/3 of the wing it has white scales or setae, which resemble fine hair. Experts point out that these mushrooms are scales with a deep division.

In this video you can see a specimen of this species:

- Predators

Even though the Megalopyge opercularis it has poisonous spines, which it uses to defend itself, this species has some predators. However, the threats are much greater during the larval phase..

Experts have observed lacewings (Chrysopa sp.) feed on eggs and larvae in their early stages. Likewise, some lizards eat caterpillars that are in the fourth instar, whose bodies measure around 5 millimeters.

On the other hand, some species of flies belonging to the Tachinidae family lay their eggs on the outside of the larvae. In this way, the fly develops inside the cocoons, forcibly opening the operculum, to be able to emerge.

Another of the insects that parasitizes Megalopyge opercularis is he Hyposoter fugitivus, which belongs to the Ichneumonidae family. This wasp attacks and kills the young larvae. Also, the female can deposit her eggs through the wall of the cocoon..

This causes the larvae of the H. fugitivus Build your own cocoons, inside the cocoon of the stuffed caterpillar. When the wasp is mature, it opens holes 2 to 3 millimeters in diameter to exit, thus killing the pupa of the stuffed caterpillar..

Habitat and distribution

Megalopyge opercularis It is found throughout the eastern United States, ranging from New Jersey to Florida and in the western region to Texas and Arkansas. Although it is very common in Florida, it reaches its highest population density in Texas, from the southern area of ​​Dallas to the western central part of that state..

It also lives in Mexico and some countries in Central and South America, including Venezuela and Argentina..

In relation to habitat, it prefers deciduous forests and the areas adjacent to them. Among the preferred tree species are elms, oaks and citrus. However, it often lives in small shrubs..


- Reproduction

The flannel moth, as this species is also known, is oviparous and has a sexual reproduction. Generally the female has two young a year. As for the mating season, it probably occurs in early summer and fall.

- Stages of development

This insect has complete metamorphosis, going through four stages throughout its life: egg, larva, pupa or chrysalis and adult.


The female usually reproduces during the night, laying her eggs for two nights in a row. These are deposited on the foliage of plants or on small branches. It does this by forming single or double curved rows, although it can also be done in patches.

The eggs are covered by the bristles on the lower abdomen of the female. As for hatching, it occurs between six and eight days after deposition.


Before cocoon formation, the larvae of the Megalopyge opercularis they can wander from the host plant to other plants that are nearby. They could even move to the buildings that are around their habitat.

Once mature, the caterpillars begin to turn their cocoons. It does this by building a thin silk frame, for which it uses its bristle cover as a support. Cocoons are found in deep grooves in the bark, on small branches, or on the underside of fallen trunks..

After the pupae have placed the outer layer of silk, they proceed to remove the soft mushrooms that cover their body. These are agglomerated and located in the hump that is in the upper part of the cocoon and in the internal area of ​​the same.

Pupae and adults

The larvae engulf approximately 16 days after having completed the cocoon. At the time when the pre-adult is almost out of the cocoon, the Megalopyge opercularis the pupal exoskeleton divides and emerges.


The caterpillar of this species can feed on a wide variety of plant species, and can include up to 41 genera. One of the favorite trees is oak, however, it is common to find it in elms, especially in Chinese elm (Ulmus parvifolia).

It is also found in almond, orange, apple, walnut, and persimmon trees. Likewise, it lives in some bushes, like the rose.

The larvae have mouthparts that allow them to chew on the leaves. Thus, they eat small pieces, opening holes in it. As for the late stages, they are sheet edge feeders. Therefore, to feed, they fold the area in front of the thorax over the leaf.

Sting and treatment

The stuffed caterpillar is considered one of the most poisonous in North America. This is due to the highly toxic substance it inoculates through its spines, which are connected to a venom gland..

In this sense, the contact of the skin with the thorns causes them to come off. Thus, they become embedded in the tissue, where the poison is released..

Immediately, grid-shaped hemorrhagic papules appear in the injured area. These produce severe pain, which may be localized to the wound or could radiate to the entire limb.

For example, if the injury is to the hand or forearm, the pain may be felt in the armpit area and in the chest. In some cases, patients describe this severe pain as if it were a heart attack..

Other symptoms include headaches, burning wound, vomiting, nausea, abdominal discomfort, and respiratory shock. Also, the presence of the poison in the body can cause fever, tachycardia, muscle spasms, low blood pressure and even seizures..


In any health situation, the best thing to do is go to a healthcare center as soon as possible. However, while this is happening, specialists recommend using adhesive tape to remove the spines that remain embedded in the skin..

Subsequently, the injured area can be washed with plenty of water and a little mild soap. Then you can apply ice packs to the affected area. This helps reduce swelling and pain..


  1. David M. Eagleman (2008). Envenomation by the asp caterpillar (Megalopyge opercularis). Recovered from
  2. Wikipedia (2020). Megalopyge opercularis. Recovered from
  3. Donald W. Hall (2012). Megalopyge opercularis. Recovered from
  4. Luisana Avilán, Belsy Guerrero, Edinovsky Álvarez, Alexis Rodríguez-Acosta (2010). Description of envenomation by the “chicken-worm” Caterpillar (Megalopyge opercularis) in Venezuela. Recovered from
  5. Forrester MB (2018). Megalopyge opercularis Caterpillar Stings Reported to Texas Poison Centers. Recovered from

Yet No Comments