Malacosoma americanumeastern tent caterpillar moth

Geographic Range

Eastern tent caterpillars, Malacosoma americanum, range throughout the eastern and central United States and are found as far west as the Rocky Mountains. (Wagner, 2005)


Eastern tent caterpillars are often found in forests and near human habitations. Between early spring and early summer, they build silk tents where branches of small trees meet. Preferred species of tree include peach (Prunus persica), cherry and plum (Prunus), hawthorne (Crataegus), and apple and crabapple (Malus domestica). They also build tents in other species of broadleaf trees and shrubs, such as ash (Fraxinus), birch (Betula), willow (Salix), maple (Acer), oak (Quercus), and poplar (Populus). Eastern tent caterpillars are active as moths from late May to June, where they can be found in a variety of habitats including landscaped properties, although they are much more abundant in wooded areas. (Costa, 1998; Drees and Jackman, 1999; Hyche, 1996; Shetlar, 2000; Wagner, 2005)

Physical Description

Adult (moth) Eastern tent caterpillars are reddish brown in color and have two creamy white stripes running obliquely across their front wings. Wingspan is approximately 2.5 cm. Adults have siphoning mouthparts, and females are generally larger than males.

As caterpillars, they can reach 4 to 5 cm in length, and their long setae give them a fuzzy appearance. Color varies, but most are black with a white dorsal stripe and brown and yellow lateral lines. Many also have blue spots along their sides. Caterpillars have chewing mouthparts, used to consume leaves.

Egg masses of Eastern tent caterpillars encircle branches and are covered with shiny, black or dark grey varnish-like material. Tents of Malacoso americanum are among the largest of any tent caterpillar and are typically constructed where two branches meet. Tents usually face southeast. Cocoons are white or yellow. (Drees and Jackman, 1999; Hyche, 1996; Mahr, 2005; Shetlar, 2000; Wagner, 2005)

  • Sexual Dimorphism
  • female larger
  • Range length
    caterpillars 5 (high) cm
  • Average wingspan
    2.5 cm
    0.98 in


Eastern tent caterpillars mate soon after emergence. Females attach eggs to branches in masses of about 150 to 400 eggs. Egg masses encircle small branches or twigs and are covered with shiny, black or dark grey varnish-like material. In about 3 weeks, embryos develop to first-stage larvae. Larvae enter diapause and spend summer, fall and most of winter unhatched. Eggs begin to hatch late February and early March, just as leaf development begins to occur. Newly hatched caterpillars feed on the egg mass covering and then move to a nearby fork in the branches where they spin silk to form a tent. Eastern tent caterpillars have 6 larval instars. After 4 to 6 weeks of feeding on leaves, caterpillars reach about 5 cm in length and are fully grown. They then leave the tent and spin a silk cocoon in a protected place such as under rocks, logs, debris on the ground, or cracks of buildings. The pupal stage lasts 3 to 4 weeks. Eastern tent caterpillars live about 5 days as adults. (Choate and Rieske, 2005; Costa, 1998; Fitzgerald, 2007)


Male Eastern tent caterpillars seek females even before females have left the cocoon, flying from cocoon to cocoon waiting for females to emerge. There are generally a higher number of males than females. Mating behavior of both males and females varies with sex ratio and population abundance. Especially when competition is high, males may attempt to mate with females that are already copulating. Increased male competition allows females to select and reject potential mates. Males may or may not hold onto the substrate while mating. Copulation generally ends shortly after a female begins fanning her wings, although if competition is high, males may prolong copulation. Females die soon after breeding. Eastern tent caterpillars are polygynangrous. (Fitzgerald, 2007; Hyche, 1996)

Eastern tent caterpillars breed once a year, mating soon after emergence. After copulation, females lay their eggs in a protected area in masses of 150 to 400 eggs. Eggs are cylindrical and measure about 1 mm in length. Eggs are placed in rows on a twig, and eggs and twig are wrapped with a frothy, shiny material called spumaline. Egg masses of Eastern tent caterpillars are easy to recognize. Eggs hatch during late February and early March, just as leaf development begins to occur. (Hyche, 1996)

  • Breeding interval
    Eastern tent caterpillars breed once a year.
  • Range eggs per season
    100 to 400

Female Eastern tent caterpillars cover egg masses with a protective substance, spumaline. The spumaline coating also serves as the first meal for hatching caterpillars. Because females die soon after breeding, they do not actively provide parental care after eggs are laid. (Hyche, 1996)


Eastern tent caterpillars live about 10 months in total. Adults may live for 5 days. Females usually die soon after laying eggs. (Fitzgerald, 2007; Hyche, 1996)

  • Average lifespan
    Status: wild
    10 months


Eastern tent caterpillars are social, and as caterpillars they live in “cohorts," which are initially formed from sibling groups. Typical sibling group size (third instar) is 50 to 200 individuals. Populations at a given time can contain sub-populations of multiple instar stages.

When not feeding, a cohort of Eastern tent caterpillars aggregates within their silken "tent." The size of the tent increases as the caterpillars grow. Tents are thought to provide shelter from parasites and from some predators as well. They also aid in thermoregulation, and tents often have zones of varying temperature, caused by effects of sun, air currents, and aggregations of caterpillars within it. Individuals within a tent have been observed to move to warmer or cooler sections of the enclosure as need for heating or cooling dictates. In situations of high ambient heat, caterpillars have been observed hanging by their prolegs from the lower surface of the tent.

Eastern tent caterpillars are among the first leaf-eaters to appear in the spring, and their emergence is synchronized with the appearance of early leaves on host trees. They typically remain in the tree on which they emerged as long as sufficient food resources are available. If supply of suitable leaves becomes marginal, or if density becomes very high, caterpillars migrate to other trees.

As Eastern tent caterpillars forage, they leave an "exploratory" trail of silk secreted from spinnerets. When they follow exploratory trails back to their tent, they may overmark the trail, creating "recruitment trails." They leave behind pheromones, deposited by dragging their abdomens, indicating where high quality food has been found. A single individual can even recruit the entire colony to a food source through this method. Movement of Eastern tent caterpillars is largely confined to trails and frequently used trails become conspicuously marked. (Fitzgerald, 2007; Reiske and Townsend, 2005; Wagner, 2005)

Home Range

Little information is currently available regarding the home range of Eastern tent caterpillars.

Communication and Perception

Eastern tent caterpillars have a well-developed system for making chemical trails, perceiving trails made by others, and reinforcing trails according to the feeding experience associated with them. An initial "exploratory" trail made by a foraging individual is recognizable by others; if the foraging path proves fruitful, reinforcing pheromones will be added to it by the original forager and subsequent trail followers, thereby recruiting others to benefit from quality food sources (a "recruitment trail"). Individuals choose a trail reinforced by more foragers over one that has had fewer reinforcers.

Caterpillars are also sensitive to light and can perceive images in at least a crude manner. Experimentation has demonstrated capability to perceive a tree-like vertical shape from modest distances as well as capability to discern a difference between objects of different reflectivity. They are also able to sense the direction of the sun. When presented experimentally with an undifferentiated barren field (an extensive asphalt surface), they move in directions that are strongly correlated with sun orientation at the time of the experiment. (Fitzgerald, 2007; Reiske and Townsend, 2005; Wagner, 2005)

Food Habits

Newly hatched Eastern tent caterpillars initially consume the coating that surrounded the egg mass. After constructing a tent, they typically leave the tent prior to dawn, evening and night to feed on leaves. They retreat to the tent between feeding bouts and to avoid midday heat or rain. Eastern tent caterpillars prefer leaves of peach (Prunus persica), plum (Prunus), hawthorne (Crataegus), apple and crabapple (Malus domestica) and cherry trees such as black cherry (Prunus serotina), pin cherry (Prunus pensylvanica), and choke cherry (Prunus virginiana). Their favored host plants are black cherry trees (Prunus serotina). If resources are limited, they may also consume leaves of other species of broadleaf trees and shrubs, such as maple (Acer), and oak (Quercus). Eastern tent caterpillars can quickly damage sections of a tree. Adults do not feed. (Costa, 1998; Drees and Jackman, 1999; Hyche, 1996; Mahr, 2005)

  • Plant Foods
  • leaves


Predation is the most significant cause of mortality in Eastern tent caterpillars. Colonies between the first and second instars are the most preyed upon, and as instar number increases, so does their survival rate. Birds are their most common predators and often destroy the tent and consume the better part of the colony. Avian predators prefer younger larvae and pupae, and final instar caterpillars are rarely attacked, presumably due to setae and toxicity. Eastern tent caterpillars also have a variety of invertebrate predators, although they generally do not destroy the entire colony.

Eastern tent caterpillars are aposematic, resting together in groups on the surface of their tent. They also thrash the anterior part of their body when predators are detected. Other caterpillars in the colony also begin to trash, which deters timid predators such as stink bugs. (Costa, 1998; Fitzgerald, 2007)

Ecosystem Roles

Eastern tent caterpillars build their tents on and consume the leaves of a variety of trees and shrubs, particularly members of the family Rosaceae such as apple and crabapple (Malus domestica) and cherry (Prunus). Their favored host plant are black cherry trees (Prunus serotina). They also have a variety of avian and invertebrate predators. Attacks of an avian predators often increase the likelihood of an invertebrate attack due to damages sustained to the tent. Eastern tent caterpillars also host a number of parasites, like Tachinid flies. Eastern tent caterpillars may fall victim to a variety of pathogens, including the viruses Clostridium and Bacillus. Disease mortality does not often parallel predation mortality, but severe outbreaks have been known to occur. (Costa, 1998)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known direct positive effects of Eastern tent caterpillars on humans. As prey for birds and invertebrates, however, they help maintain a forest ecosystem.

Economic Importance for Humans: Negative

A single colony of Eastern tent caterpillars can completely defoliate small ornamental trees, and heavy infestations can cause serious damage to larger trees. Damage to already weakened trees can be fatal. Tents are considered unsightly and are thus removed by land owners. For aesthetic reasons, this species can be considered a pest, particularly to outdoor recreational areas. Eastern tent caterpillars are also serious pests in apple orchards, and many pest-management programs have considerably reduced their presence in orchards. Additionally, Eastern tent caterpillars are associated with Mare Reproductive Loss Syndrome (MRLS). MRLS caused approximately 330 million US dollars in losses in 2001. (Hyche, 1996; Mahr, 2005; Shetlar, 2000; Webb, et al., 2004)

Conservation Status

Although pest-management programs are in place in many orchards and sunburn recreational areas, Eastern tent caterpillars are not threatened. This species has not been evaluated by the ICUN or the US Fish & Wildlife Service.


Yami Martinez (author), Rutgers University, John McDermott (author), Rutgers University, Jennifer Oberle (author), Rutgers University, Jay Parikh (author), Rutgers University, David V. Howe (editor), Rutgers University, Gail McCormick (editor), Animal Diversity Web Staff.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in landscapes dominated by human agriculture.


having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


uses smells or other chemicals to communicate


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.


active at dawn and dusk


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


union of egg and spermatozoan


an animal that mainly eats leaves.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


chemicals released into air or water that are detected by and responded to by other animals of the same species


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


living in residential areas on the outskirts of large cities or towns.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


living in cities and large towns, landscapes dominated by human structures and activity.


uses sight to communicate


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Choate, B., L. Rieske. 2005. Life History and Age-Specific Mortality of Eastern Tent Caterpillar (Lepidoptera: Lasiocampidae). Ecology and Population Biology, 98(4): 496-502.

Costa, J. 1998. Larval Ontogeny and Survivorship of Eastern Tent Caterpillar Colonies. Journal of Research on the Lepidoptera, 32: 89-98.

Drees, B., J. Jackman. 1999. "Texas Cooperative Extension" (On-line). Eastern Tent Caterpillar. Accessed December 08, 2007 at

Fitzgerald, T. 2007. "The eastern tent caterpillar (Malacosoma americanum) (Lasiocampidae)" (On-line). Social Caterpillars. Accessed January 22, 2007 at

Hyche, L. 1996. "The Eastern Tent Caterpillar: A Guide to Recognition and Habits in Alabama" (On-line). Accessed December 09, 2006 at

Mahr, S. 2005. "Eastern Tent Caterpillar, Malacosoma americanum" (On-line). Wisconsin Master Gardener Program. Accessed December 09, 2006 at

Reiske, L., L. Townsend. 2005. Orientation and dispersal Patterns of the Eastern Tent Caterpillar, Malacosoma americanum. Journal of Insect Behavior, 18(2): 193-207.

Shetlar, D. 2000. "Eastern and Forest Tent Caterpillars and their Control" (On-line). The Ohio State University Extension Factsheet. Insect and Pest Series.. Accessed December 09, 2006 at

Travis, H. 2004. The Effect of Eastern Tent Caterpillar (Malacosoma americanum) on Fall Webworm (Hyphantria cunea) Selection of Black Cherry (Prunus serotina) as a Host Tree. American Midland Naturalist, 153: 270-275.

Wagner, D. 2005. Caterpillars of Eastern North America. Princeton, NJ: Princeton University Press.

Webb, B., W. Barney, D. Dahlman, S. DeBorde, C. Weer, N. Williams, J. Donahue, K. McDowell. 2004. Eastern tent caterpillars (Malacosoma americanum) cause mare reproductive loss syndrome. Journal of Insect Physiology, 50(2-3): 185-193.