Tent Caterpillar: All You Need to Know for Effective Control

Tent caterpillars are fascinating creatures that you might come across in your backyard or on a nature walk. These caterpillars are known for their unique behavior of building silk “tents” in the branches of trees for shelter. While they might seem harmless, tent caterpillars also have a reputation for damaging and defoliating trees as they feed on their leaves.

You’ll find different species of tent caterpillars in North America, such as the Eastern Tent Caterpillar and the Forest Tent Caterpillar. They are easily identifiable by their distinct markings, with the Eastern Tent Caterpillar sporting a white line down its back and light blue and black spots on its sides. On the other hand, the Forest Tent Caterpillar has white footprint-shaped marks down its back and light blue stripes on its sides.

Understanding more about these intriguing insects can help you appreciate their place in the ecosystem and their role in our natural environments. So, let’s dive deeper into the world of tent caterpillars and discover what makes them so unique!

What are Tent Caterpillars

Characteristics

Tent caterpillars are hairy, social caterpillars known for creating distinctive silky nests or “tents” on the branches of trees. These tents serve as a protection for the larvae from predators and harsh weather. The caterpillars come in different types, such as eastern, forest, and western tent caterpillars.

Eastern tent caterpillars have a dark head and a prominent white or yellow stripe down the body. Forest tent caterpillars are about 2″ long at maturity, with a bluish body and a row of white or yellow keyhole-shaped markings. Western tent caterpillars are dark with orange and black markings.

Classification

Tent caterpillars belong to the genus Malacosoma, which are part of the family Lasiocampidae. The main species of tent caterpillars are:

• Eastern Tent Caterpillar (Malacosoma americanum)
• Forest Tent Caterpillar (Malacosoma disstria)
• Western Tent Caterpillar (Malacosoma californicum)

Each of these species has unique characteristics that help you identify them. The comparison table below illustrates their differences:

As the caterpillars undergo their life cycle, they transform from eggs into larvae, feed on the host plant, and eventually become adults. During the larval stage, they are voracious eaters and sometimes defoliate trees. These tent caterpillars are often considered a nuisance to trees and human activities but play a significant role in the ecosystem as they are a food source for many predators.

Habitat

Tent caterpillars can be found in various regions across the United States, primarily infesting deciduous trees. Examples of their preferred habitats include cherry trees and birch trees.

These caterpillars are particularly drawn to trees in sunny locations, as they require warmth and sunlight for optimal growth. In addition to cherry and birch trees, tent caterpillars are also known to infest other deciduous trees, such as:

• Oaks
• Maples
• Willows
• Poplars
• Apples

By understanding the preferred habitats of tent caterpillars, you can more effectively monitor your trees for infestations and take necessary action to protect them. Remember, early detection and intervention are key in managing these pests and minimizing the damage they cause.

Diet and Feeding Habits

Eastern tent caterpillars are known to feed on the leaves of fruit trees, such as apple, chokecherry, crabapple, plum, and cherry during May and June source. As they eat, they may sometimes defoliate the trees.

The forest tent caterpillar, on the other hand, does not make a tent and is typically found in wooded areas, feeding on oak, poplar, maple, or birch trees source. These caterpillars may become a serious pest in some circumstances.

In general, you will notice that both types of tent caterpillars have strong foraging habits, feeding primarily on the leaves of their host trees. To give you a better understanding, here’s a comparison table of the two species:

Caterpillars of both species usually gather in groups while feeding, making their presence quite noticeable.

By understanding their diet and feeding habits, you can better manage these tent caterpillar populations in your garden or wooded area to protect your trees.

Reproduction

Mating Behavior

The lifecycle of tent caterpillars begins with mating. Adult moths, which are light brown with faint light wavy bands on their wings, emerge about two weeks after pupation¹. The adult moths are responsible for mating and reproducing in order to ensure the continuation of the species. During the mating process, male and female moths engage in courtship behaviors and release pheromones to attract their mates.

Egg Laying

Once the female tent caterpillar moth is fertilized, it searches for a suitable location to lay its eggs. Eastern tent caterpillars, forest tent caterpillars, and western tent caterpillars are different species of tent caterpillars but share similarities in their reproductive patterns. After mating, female moths lay clusters of eggs on tree branches². These eggs are covered with a protective layer that can help them survive during winter.

As spring arrives, the eggs hatch, releasing young caterpillars that begin to build tents from silk as they feed on the foliage of their host trees³. Eastern tent caterpillars, in particular, have been associated with mare reproductive loss syndrome⁴. This is a condition where pregnant mares suffer late-term abortions or give birth to weak foals after ingesting the toxins present in the caterpillars while grazing⁴.

To summarize, the reproductive process of tent caterpillars involves:

• Mating between adult moths
• Egg-laying by fertilized females on tree branches
• Hatching of eggs in spring, leading to the emergence of young caterpillars

By understanding the reproductive behaviors of tent caterpillars, you can better appreciate their lifecycle, as well as the concerns associated with their infestation in certain areas.

Impact on Trees and Their Environment

Specific Damage Identification

Tent caterpillars, including eastern tent caterpillars and forest tent caterpillars, can cause significant damage to trees in their environment. The primary sign of infestation is the presence of webs on branches, containing caterpillars feeding on leaves. They primarily attack deciduous trees such as cherry, oak, and sugar maple. The caterpillars consume the leaves, causing defoliation and stress to the tree.

Once you spot these webs and caterpillars, inspect the tree for further damage. Heavy infestation can lead to complete defoliation, which weakens the tree and makes it more susceptible to diseases and pests. You may notice some tree species losing branches as they struggle to recover from the effects of the caterpillars’ feeding.

Effects on Ecosystem

Tent caterpillar infestation can impact not only individual trees but also the broader ecosystem, especially in parks and forests. As they damage the trees, they disrupt the balance of the ecosystem, which in turn affects other organisms living in the area. The loss of leaves can change the microclimate and reduce the habitat for other species.

For example, defoliated trees produce less oxygen and absorb less carbon dioxide, making their contribution to the ecosystem less effective. It also increases the probability of erosion, potentially leading to long-term consequences for soil quality and biodiversity. If not controlled, tent caterpillar infestations can have lasting effects on the health and stability of these ecosystems.

In summary, it’s essential to identify and manage tent caterpillar infestations to preserve the health of individual trees and the ecosystem. Pay close attention to the trees in your area and take action to mitigate the damage caused by these caterpillars.

Control Measures

Natural Predators

Tent caterpillars have various natural predators that help keep their population in check. These predators include over 100 species of parasitic tachinid flies and wasps that target their eggs, larvae, and pupae (source). Additionally, predaceous beetles, bugs, and birds consume the eggs, larvae, and moths.

Biological Control Methods

One effective biological control method you can use to keep tent caterpillar populations under control is Bacillus thuringiensis (Bt), a naturally occurring bacterium that acts as a selective insecticide. When tent caterpillar larvae consume the bacteria, it kills them by attacking their digestive systems. Bt is safe for humans and non-target organisms like beneficial insects (source).

Another method to control tent caterpillars is disrupting their pheromone trails. By applying a pheromone-based lure, you can interfere with the caterpillars’ ability to locate and feed on their host plants, thus reducing their population.

Preventive/Proactive Measures

Taking preventive or proactive measures can help you manage tent caterpillar infestations more effectively. Some measures you can take include:

• Regularly inspecting your trees for the presence of egg masses or tents
• Removing and destroying tents and egg masses manually or by pruning infested branches
• Encouraging natural predators by providing a diverse habitat with various plants and nesting sites for beneficial insects and birds
• Planting tree species resistant to tent caterpillar infestations, such as ash, maple, and oak, as they are less likely to be severely affected than other tree species (source)

Common Species in the United States

Eastern Tent Caterpillar

The Eastern Tent Caterpillar (Malacosoma americanum) is a common species found in the eastern United States. They are known for their visible, silk tents that can be found on branches of various hardwood trees like cherry and apple. Some key features of Eastern Tent Caterpillars include:

• Black body with white stripes
• Blue and orange markings on the sides
• Long, fine hairs covering their bodies

Their feeding habits mainly involve eating leaves of their host trees, which may result in defoliation if left unchecked.

Forest Tent Caterpillar

The Forest Tent Caterpillar (Malacosoma disstria) is another common species found across the United States. Unlike their eastern counterparts, they do not make tents but create silk mats on branches and trunks to rest and molt. Some characteristics of Forest Tent Caterpillars are:

• Blue and white body with black lines
• Distinctive keyhole-shaped white spots on the back
• Prefer deciduous trees like oaks, aspen, and sugar maple

Although they can cause defoliation, they are generally less harmful to trees compared to Eastern Tent Caterpillars due to their shorter feeding period.

Western Tent Caterpillar

The Western Tent Caterpillar (Malacosoma californicum) inhabits western regions of the United States. Like Eastern Tent Caterpillars, they create silk tents in tree branches. Some features of the Western Tent Caterpillars include:

• Yellow-brown body with a dark stripe
• Bluish markings on the sides
• Host to a wide range of trees, including deciduous and coniferous species

Here is a comparison table for these three species:

In dealing with these common tent caterpillar species, it’s crucial to monitor your trees and take necessary actions, such as removing tents or treating affected areas with appropriate solutions to ensure the health of your landscaping.

Common Myths and Misconceptions

Myth 1: Tent caterpillars are dangerous to humans.
In reality, they are harmless to people. While their hairs might cause mild skin irritation for some, they are not venomous or harmful to touch.

Myth 2: They are the same as gypsy moths or worms.
Tent caterpillars and gypsy moth caterpillars are different species. A major distinction is that gypsy moth caterpillars don’t create tents, while tent caterpillars do. As for worms, tent caterpillars are not worms; they’re insects in the Lepidoptera family.

Myth 3: Tent caterpillars only feed on poplar trees.
Although they’re often found on poplar trees, they also eat leaves from other fruit and shade trees.

Here’s a comparison table showing the differences between tent caterpillars and gypsy moths:

Lastly, it’s important to understand that while tent caterpillars may look unpleasant and cause some damage to trees, they are a natural part of the ecosystem. In most cases, their presence doesn’t warrant panic or excessive control measures. However, be observant and monitor their population to avoid severe infestations that could harm your trees.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Tea Oil Caterpillar from India

Subject: BIG Caterpillar..
Location: Goa, India
May 21, 2012 12:36 pm
Hi, This beauty frightened the life out of a clothing stall-holder while i was walking past. The photo was taken in January 2012 in the state of Goa in India, and i’d love to know what kind of butterfly/moth it would eventually turn in to. The length was a very impressive six or seven inches!!
Thanks for your help 🙂
Signature: Mike

Hi Mike,
This Moth Caterpillar looks very familiar and we believe there is another example in our archives, however we cannot remember what it was identified as and we didn’t have any luck finding it in our initial attempt.  When time permits, we will return to your identification request.  Perhaps one of our readers will have better luck and post a comment.

Ed. NOte:  Thanks to a tip from lepidopterist Julian Donahue, we were informed that this is a Lappet Moth Caterpillar in the family Lasiocampidae.  We narrowed our search in the archives and located a match with the Tea Oil Caterpillar submitted from Malaysia a year and a half ago.

Letter 2 – Possibly Tea Oil Caterpillar from Malaysia

Giant Caterpillar

Giant Caterpillar
Location: Rainforest Discovery Centre, Sandakan, Sabah, Malaysia.
December 17, 2010 4:02 am
My sister found this giant caterpillar in RDC – Rainforest Discovery Centre.
I had measured it with my ruler, it is 11cm long.
It is quiet, doesn’t move much.
This is the largest caterpillar I had ever seen, is this a world record ?
Signature: C.X. Wong

Dear C.X. Wong,
While we do not recognize your Caterpillar, we will post the images and hopefully one of our readers will be able to provide some input.  We are uncertain what the largest caterpillar in the world might be, but the Hickory Horned Devil is the largest North American Caterpillar according to BugGuide.  According to Green Answers, it can grow to 14 centimeters, which is larger than the specimen in Malaysia.

Ed. Note: December 18, 2010
We received a comment yesterday that this is the caterpillar of Lebeda nobilis Walker,1855.  We did a web search of that name and found an Asian website with images of the life cycle and the caterpillar matches somewhat. Another Asian website has images that seem to be a closer match.  The caterpillar is also pictured on Bettaman’s Photostream on Flickr. We found a journal posted online with no images that associates the common name Tea Oil Caterpillar with this species.  Even if this is not the correct species, the resemblance is quite close and probably indicates that the family Lasiocampidae, the Tent Caterpillars and Lappet Moths, is correct.

Letter 3 – Toothed Cream Spot Eggar Caterpillar and Cocoon from South Africa

Subject: Unknown Caterpillar
Location: North east coast of South Africa
June 9, 2014 4:10 am
We found this guy eating on the tree and then began spinning a cocoon around himself. Amazingly the next morning the cocoon was complete with the hairs from the caterpillar embedded into the surface.
Signature: Brian

Hi Brian,
We believe this is a Lappet Moth Caterpillar in the family Lasiocampidae, and we did find what appears to be a matching image on iSpot that is identified as a Toothed Cream Spot Eggar, Catalebeda cuneilinea, but we have not been able to locate any other images online to verify that identification.