Forest Tent Caterpillar: All You Need to Know in a Nutshell

The Forest Tent Caterpillar is a native insect found in hardwood forests throughout North America. These caterpillars are particularly abundant in eastern regions and are known to play a significant role in the ecosystem. In this article, we will discuss the essential aspects of this fascinating creature, including its life cycle, feeding habits, and impact on its environment.

This species feeds on a variety of broad-leaved trees and shrubs that vary depending on the region. For example, they are commonly found on trees such as oaks, aspens, basswoods, and birches. Interestingly, Forest Tent Caterpillars can also feed on fruit trees and cause substantial damage to them.

Although they may sound harmful, these caterpillars are a vital part of the food chain. Their feeding activities reduce the growth rate of certain trees, which can influence the overall health of the forest. And just like any other organism, Forest Tent Caterpillars have their own predators, such as birds and insect-eating mammals. Understanding the dynamic balance they create within their ecosystem will give us a clearer perspective on these fascinating creatures.

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Identification and Habitat

Physical Characteristics

Forest tent caterpillars, unlike their name suggests, do not create tents. The caterpillars have a distinct appearance, characterized by blue and black bodies, with a row of white footprint-shaped markings along their backs, bordered by blue stripes1. They may grow up to 2 inches long during their larval stage.

Host Trees and Foliage

Forest tent caterpillars primarily feed on the leaves of a variety of deciduous trees, some examples include:

  • Oak
  • Birch
  • Ash
  • Willow

Other host trees consist of quaking aspens, balsam poplar, basswood, and fruit trees2. Additionally, they have been known to target sweet gum, black gum, and tupelo trees in certain regions3.

TreesAbundance
OakHigh
BirchHigh
AshHigh
WillowModerate

Forest tent caterpillars consume leaves and damage their host trees. Defoliation can slow down a tree’s growth rate2. In cases where the target trees are entirely stripped of leaves, these caterpillars may also feed on shrubs and vegetables3.

Life Cycle and Behavior

Eggs and Larval Stage

The life cycle of the Forest Tent Caterpillar begins with eggs, which are laid in a mass wrapped around the twigs of trees and shrubs1. Caterpillars, also known as larvae, emerge from these egg masses in early to mid-May2. These caterpillars feed actively on aspen and other broadleaf trees for five to six weeks2. Some common tree species include oaks, sweet gum, black gum, and tupelo3. Occasionally, caterpillars also feed on shrubs and vegetables3.

During this larval stage, caterpillars molt several times before reaching their final size.

Pupation and Adult Moths

Once caterpillars have reached their final size, they begin the process of pupation. They form cocoons, with the caterpillar developing into a pupa inside it. After a couple of weeks, adult moths emerge from the cocoons4. These adult moths mate and lay eggs, continuing the life cycle of the Forest Tent Caterpillar4.

Table 1: Comparison between larvae and adult moths

| Stage        | Appearance   | Feeding Habits        |
|--------------|--------------|-----------------------|
| Larva        | Caterpillar  | Feed on tree leaves   |
| Adult Moth   | Winged insect| Do not feed           |

Here is a summary of characteristics of the Forest Tent Caterpillar’s life cycle in bullet points:

  • Egg masses are laid around tree twigs
  • Larvae emerge and feed on various tree leaves
  • Larvae molt several times before pupation
  • Cocoons are formed for pupation
  • Adult moths emerge from cocoons

Impact on Trees and Environment

Commonly Affected Trees

Forest tent caterpillars primarily attack a variety of broadleaf trees, such as:

  • Quaking aspens
  • Balsam poplar
  • Basswood
  • Oaks1
  • Ashes
  • Birches
  • Alder
  • Fruit trees including cherry and plum2.

Defoliation and Damage

Defoliation is a major outcome of the forest tent caterpillar infestation. These caterpillars consume leaves, leading to slowed growth rates in affected trees3. In severe cases, they may also cause damage to surrounding conifers and hardwood trees4.

Table 1: Comparison of Defoliation Effects in Affected Trees

Tree TypeDefoliation Impact
MapleModerate impact on growth rates5
ElmSevere impact, possibly leading to tree death6

Control and Prevention

Cultural and Mechanical Controls

  • Pruning: Remove infested branches and twigs with visible egg masses or tents. This prevents the caterpillars from damaging the host tree.
  • Manual removal: Use gloves and remove the caterpillars by hand from the tree trunks and branches. Dispose of them in a bucket of soapy water to kill them.

Forest tent caterpillars primarily attack broadleaf trees like oaks, aspens, and tupelos, causing defoliation and slowed growth rates. They can also cause damage to shrubs and fruit trees. Identifying the nests and removing them early in the larval stage can help minimize damage to your trees.

Chemical and Biological Controls

  • Bacillus thuringiensis (Bt): This is a bacteria-based insecticide that targets the eastern and western tent caterpillar. It is applied during the early larval stage to be most effective. Bt is less harmful to the environment and natural enemies of the caterpillars.
  • Other insecticides: Chemical insecticides, like pyrethroids, can be applied to control caterpillar populations. Always follow label instructions and consult with a local extension office for specific recommendations.

In North America, natural enemies of the tent caterpillar include parasites, diseases, and predatory insects. Encouraging these beneficial organisms can provide additional control measures.

Control MethodProsCons
Pruning and manual removalEnvironmentally friendly, cost-freeTime-consuming, labor-intensive
Bacillus thuringiensis (Bt) applicationTargets specific pests, eco-friendlyMust be applied early in larval stage, not effective on all caterpillar species
Other insecticidesFast-acting, broad-spectrum controlCan harm natural enemies, potential pesticide resistance

Remember to monitor your trees and shrubs for early signs of infestation. Act quickly when you spot forest tent caterpillars, and use a combination of cultural, mechanical, and chemical controls where appropriate.

Interactions with Other Species

Predators and Diseases

Forest tent caterpillars experience predation from a variety of animals and face several diseases. Some predators include:

  • Birds
  • Small mammals
  • Insects

Additionally, they can be affected by diseases like viral, bacterial, and fungal infections. These natural enemies play a crucial role in controlling caterpillar populations, minimizing outbreaks and defoliation events.

Caterpillar Comparisons

There are several differences between forest tent caterpillars and their close relative, the eastern tent caterpillar. Here’s a comparison table to highlight their differences:

FeatureForest Tent CaterpillarEastern Tent Caterpillar
AppearanceSpots along the backWhite stripe down the back
Host plantsAspens, oaks, birchPeach, hawthorn, elm
Period of pupationMayLate May to early June

Some notable differences in their interactions with other species include:

  • Both caterpillars primarily feed on different host plants, with forest tent caterpillars favoring aspens, oaks, and birch, while eastern tent caterpillars prefer peach, hawthorn, and elm trees.
  • While both caterpillars suffer from predation and disease, eastern tent caterpillars are more susceptible to starvation during droughts, as their host plants are less resilient to dry conditions.
  • In terms of appearance, forest tent caterpillars have spots along their backs, whereas eastern tent caterpillars exhibit a distinctive white stripe. This difference in appearance can affect their predation rates, as certain predators may prefer one type of caterpillar over the other.

Footnotes

  1. https://entnemdept.ufl.edu/creatures/trees/forest_tent_caterpillar.htm 2 3

  2. https://extension.umn.edu/yard-and-garden-insects/forest-tent-caterpillars 2 3 4 5

  3. https://content.ces.ncsu.edu/forest-tent-caterpillar 2 3 4 5

  4. University of Florida – IFAS Extension 2 3

  5. Wisconsin DNR

  6. Umd Extension

  7. Wisconsin DNR

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 – Tent Caterpillars in Joshua Tree

April 2, 2010
We took the day off yesterday and went to Joshua Tree National Park to see the desert in bloom, and we saw gorgeous wild flowers in the low desert.  Alas, we saw virtually no insects except a few honey bees and some nondescript flies that refused to sit still long enough for a photo.  We did take several poor photos of these Tent Caterpillars which were quite plentiful.  We believe they are Southwestern Tent Caterpillars, Malacosoma incurvum, which is pictured on BugGuide, though they might also be California Tent Caterpillars, Malacosoma californicum, also pictured on BugGuideMila Zinkova’s image on Wikimedia Commons puts our photo to shame, and she visited Joshua Tree exactly a year before our own visit.

Tent Caterpillars

Letter 2 – Western Tent Caterpillars

Can you help identify these Caterpillars
Sat, May 23, 2009 at 8:33 PM
Dear Bugman,
I recently found a silk nest filled with these black-brown caterpillars. They have rusty hair covering their bodies and have distinctive white and orange markings. The orange markings in a triangular shape and there are 2 to each segment of their bodies. the white markings are found along their sides as well as down the top of their bodies between the orange markings. Several people have said they could be Painted Ladies, yet they really don’t resemble any pictures I have found.
Thank you for your help
Penny
Kelowna British Columbia, Canada

Western Tent Caterpillars in Captivity
Western Tent Caterpillars in Captivity

Dear Penny,
We regret to inform you that these are not Painted Lady Caterpillars, nor any other lovely butterfly, but rather, they are Western Tent Caterpillars, Malacosoma californicum, which can be viewed on BugGuide.  The larvae are social and gregarious feeders that construct silken nests for protection when not feeding.  Here is what the Washington State University Biology and Control of Tent Caterpillars website indicates:  “The western tent caterpillar ( Malacosoma californicum pluviale Dyar) is often the most numerous in western Washington. Its orange and black markings are familiar to many people. This species spins tents on the tips of branches. The eggs hatch in early spring just as the new buds break in April or May. The young larvae begin feeding in groups. The larvae of both species molt (shed their skins) four times during their 5- to 6-week growing period.
As the caterpillars mature, they begin to feed in small groups or singly. Just before they spin their cocoons in mid-June, they crawl about looking for a protected place in plants or on structures to attach their cocoons. The adult moths emerge in approximately 7 to 10 days. The moths are stout-bodied and light brown. They often fly in clusters around street or porch lights on summer evenings. After the moths mate, the females lay 100 to 350 eggs in a froth-covered band around small twigs or branches of host trees. The eggs mature in 3 weeks but do not hatch until the following spring.
Tent caterpillars are primarily a nuisance. They do not transmit diseases to humans, do not bite, and are not poisonous. During years when large numbers of these caterpillars hatch, they can cause slippery roads and walks when they leave the trees.
Benefits of a caterpillar outbreak can be numerous in a natural setting. While caterpillars are distasteful to most birds, some birds feed on them. When alders and other trees are defoliated, the shrubs and trees below receive increased sunlight, giving some of them a boost in growth. The eaten leaves pass through the caterpillar’s body and emerge as little pellets which can break down easily, returning nutrients to the forest floor. Pupae provide nutritious meals for small mammals, and moths are eaten by birds and bats.
Where trees are crowded or stressed, the defoliation could be a life and death matter. Weak trees may die; healthy trees will leaf out again. In a natural setting, surviving trees can prosper in the absence of competition.
Healthy ornamental trees and shrubs should survive even serious defoliation. Trees which have been under stress (excess cold, heat, crowding, drought, flooding, etc.) may succumb and require more protection.
Natural Enemies
Tent caterpillars have numerous enemies. One is a tachinid fly which parasitizes the larvae by depositing white eggs on the caterpillar’s body. When the egg hatches, a small maggot burrows into the caterpillar and begins feeding. Tent caterpillars are also subject to a virus disease called wilt. While such natural enemies will reduce the number of tent caterpillars eventually, this process is gradual and may take 2 or more years. During that time, the affected trees may suffer such severe damage, that they will not recover. “

Western Tent Caterpillars

Letter 3 – Eastern Tent Caterpillar Invasion in Maryland

Subject: Gypsy Moth?
Location: Middletown, MD
May 11, 2014 2:32 pm
Hello again! Today we have been inundated by a huge number of these caterpillars on and around our house. We are in Frederick Co, MD. I was hoping you might be able to identify them for me :-).
Signature: Thank you!! Chadrenne

Eastern Tent Caterpillar
Eastern Tent Caterpillar

Dear Chadrenne,
This is an Eastern Tent Caterpillar,
Malacosoma americana, and according to BugGuide:  “larvae feed on leaves of many trees and shrubs but particularly members of the rose family such as apple, cherry, and crabapple.”  According to the Clemson University website:  “Eastern tent caterpillars typically feed during the day time and return to the nest at evening. They may remain in the nest during bad weather. These caterpillars are aggressive feeders and may strip a tree or major branches of all foliage. If the trees are otherwise healthy, the trees will normally produce new leaves. However, overall growth may be retarded due to the defoliation. This damage may significantly stress trees after three or four years of leaf loss.”  In the past week, we have received reports of large numbers of Caterpillar Hunters known as Fiery Searchers from both nearby Virginia and Missouri, and in one instance we responded by stating:  “Perhaps populations are peaking this year because there is a significantly larger proportion of prey, namely caterpillars and other insects.”  Your report of large numbers of Eastern Tent Caterpillars, a favorite prey of the Fiery Searchers, might explain the large population of the predators.

Update:  May 18, 2014
Subject: Tent Caterpillar Update
Location: Middletown, MD
May 18, 2014 9:13 am
I took this today on our Bradford Pear tree…
Signature: Chadrenne

Eastern Tent Caterpillars
Eastern Tent Caterpillars

Hi Chadrenne,
Thanks so much for the update.  The image of the individual you sent last week is a perfect image to identify the species, but your aggregation images are much more typical of the social behavior of the Eastern Tent Caterpillar.  Since we suspect this year might bring significant populations of Eastern Tent Caterpillars, we are featuring your posting.

Eastern Tent Caterpillars
Eastern Tent Caterpillars

Letter 4 – Eastern Tent Caterpillar

Eastern Tent Caterpillars
Here is a picture I took while hiking along the C&O canal in Maryland. These things are EVERYWHERE and until I took a look at your site, I thought they were Gypsy Moth Caterpillars. My 4 year old son and I were at the National Zoo the other day and while the elephants couldn’t hold his attention, he was facinated by these caterpillars inching along all over the place. He then collected several and gently placed them on his shirt and then proceeded to strut around the zoo covered in them like some caterpillar tamer on Animal Planet. Alas, I did not have my camera with me that day. Thanks for the great site!
Tracy

Hi Tracy,
Thanks for your touching story. We have recently received several images of individual Eastern Tent Caterpillars, Malacosoma americanum, but we have not posted them. Your photo is a textbook example for identification purposes.

Letter 5 – Forest Tent Caterpillar

Ed. Note: Please use our official submission form for every photo sent to our website.  The form has the disclaimer about our right to publish your letters and images.  We learned about 8 hours after this image was published that it was not submitted by the photographer.  Since we have no entomologists on staff, many of the images we receive need to be researched.  We are very reluctant to spend valuable time researching the identity of creatures that we will not be able to publish photos of on our site.  We have countless images available to the web browsing public because so many of our readers now have access to wonderful cameras (and cellular telephones that take pretty good photos as well) and we are thrilled to be able to compile them in a haphazardly organized fashion in our voluminous archives.  Though our writing staff tries its best to be bright, witty and charming, we realize that most web browsers want nice images to accompany the information they are trying to research.

Vermont caterpillar??
Hi Daniel,
Wondering if you can tell me what this caterpillar will turn into!!
Thanks, KT
PS…. I had 3 Luna Moths visit me this week, and got some really good pix. Let me know if you’d like any….

Forest Tent Caterpillar

Dear KT,
This is a Forest Tent Caterpillar,
Malacosoma disstria, and it is found throughout North America including Canada, but it is more common east of the Mississippi River according to BugGuide, where the life cycle is described as:  “One generation per year; larvae spin silken mats on tree trunks and large branches where they congregate to molt or rest from feeding; larvae also deposit silk in strands along which they travel to and from feeding sites; overwinters as larva in masses surrounding tree branches. (Unlike Eastern Tent Caterpillar, this species does not form silken tents.)”.We have no shortage of Luna Moths this year, and we are much happier to have received this particular photo because we promote the diversity of insect life on our website.

Hi again, Daniel,
I was thinking more about the photo, and I can’t imagine my friend will mind that it’s on your site. I took it from her Facebook page, so in a sense, it’s already “public”. I did write to her and sent her your reply to my question. I’m sure she’ll be happy to have the identification.
Go ahead and leave it up on your site, but can you please give photo credit to Jane A. Lindholm? That would be great. I’ll write again if there are any objections on her part.
Thanks!
KT

Hey Daniel,
Just wanted to let you know that Jane wrote to me from Wales. She’s totally fine with her photo being on your site, and was thrilled to DISCOVER your site and to find out what that caterpillar is.
All’s good!
Cool photo of a Cecropia moth my friend Joanne took tonight here in SE Vermont! If by any chance you want to use it, I’ll have her submit it the correct way!
KT

UPDATE:  August 18, 2011
Use of pic for Illinois FFA Forestry contest
August 18, 2011 2:26 pm
Dear Whats That Bug, I am looking for permission to use a few images for use in a FFA forestry contest. The image would be printed once, laminated and used for the contest and for educational purposes only. The pics that I would like to use are at the following url.
wp-content/uploads/2011/06/forest_tent_caterpillar_kt.jpg
Date of the contest is September 20, 2011.
Since the site made me place a pic in the image place, I did! Some sort of flocked insect taken last year while pruning a walnut plantation.
Thank you,
Jim Kirkland
Interim Director
University of Illinois
Illinois Forest Resource Center
jakirk@illinois.edu
Signature: Jim Kirkland

Mating Periodical Cicadas

Dear Jim Kirkland,
Please explain how the photo will be used.  It obviously cannot be entered in the contest by anyone but Jane who took the photo.  The photo you attached depicts mating Periodical Cicadas.

Dear Daniel,
The photo (wp-content/uploads/2011/06/forest_tent_caterpillar_kt.jpg ) would be printed on a  letter sized piece of paper, laminated and used as one of ten questions on a high school FFA forestry contest.  The portion of the test is titled Tree/Forest Disorders, the national FFA (Future Farmers of America) organization is the organizer of this event.   The students would have to identify the insect pest out of a list.  I was not looking to get my mating cicadas identified.  The web interface that your site uses would not let me send the question without downloading something.  However, how about checking out the flocked insect I have loaded up today.
Thank you,
Jim Kirkland
University of Illinois
Illinois Forest Resource Center

You have our permission to use the image of that purpose.  Here is a higher resolution file.
Daniel

Letter 6 – Forest Tent Caterpillars

Subject: Moth or caterpillar ?
Location: Lake Jackson Tx
April 3, 2016 2:34 pm
Spotted a very large batch of worms on a tree here on the Texas gulf coast,
Wondering as to what they are, moth, caterpillar or butterflies…. Just curious, thanks in advance!
Signature: Curious Rae

Eastern Tent Caterpillars
Forest Tent Caterpillars

Dear Curious Rae,
Your image of a group of Eastern Tent Caterpillars as well as a marvelous close-up of an individual are an excellent addition to our archives.  Folks wanting to make identifications can view documentation of both details of the individual and the group aggregating behavior for the species.  You can find out some wonderful information on the Eastern Tent Caterpillar on the State University of New York at Cortland site devoted to Social Caterpillars maintained by Terrence D. Fitzgerald where it states:  “In terms of complexity of interactions, eastern tent caterpillars stand near the pinnacle of caterpillar sociality. The adult moth lays her eggs in a single batch in late spring or early summer.  Oviposition is limited to cherry, apple and a few other rosaceous trees.  The egg masses contain on average 200-300 eggs. mothEmbryogenesis proceeds rapidly and within three weeks fully formed caterpillars can be found within the eggs. But the small caterpillars lie quiescent  until the following spring, chewing their way through the shells of their eggs just as the buds of the host tree begins to expand.first tent  The newly hatched caterpillars initiate the construction of a silk tent soon after emerging.  The caterpillars typically aggregate at the tent site for the whole of their larval life, expanding the tent each day to accommodate their increasing size. Under field conditions, the caterpillars feed three times each day, just before dawn, in the evening after sunset, and at mid afternoon. During each bout of feeding the caterpillars emerge from the tent, add silk to the structure, move to distant feeding sites en masse, feed, then return immediately to the tent where they rest until the next activity period. The exception to this pattern occurs in the last instar when the caterpillars feed only at night. The caterpillars lay down pheromone trails to guide their movements between the tent and feeding sites. The insect has six larval instars.  When fully grown, the caterpillars disperse and construct cocoons in protected places.  The adults emerge about two weeks later.  Mating and oviposition typically occur on the same day as the moths emerge from their cocoons and being completely spent the females die soon thereafter.”

Eastern Tent Caterpillar
Forest Tent Caterpillar

Update:  April 5, 2016
Thanks to a comment from Ben, we agree that this is a Forest Tent Caterpillar,
Malacosoma disstria, a different species in the same genus.  According to BugGuide:  “Larvae: dark-gray to brownish-black background body color, highlighted by broad, pale-blue lines and thin, broken yellow lines extending along each side” and “Eastern Tent Caterpillar (Malacosoma americanum) has an unbroken cream/white line along its back, and a dark face.”

Letter 7 – Forest Tent Caterpillar

Blue/turquiose caterpillar
Location: Nashville, Tennessee
April 17, 2012 11:29 pm
What kind of caterpillar is this? I found him in my backyard a couple of weeks ago crawling on some mulch.
Signature: Suzanne

Forest Tent Caterpillar

Dear Suzanne,
This beautiful caterpillar is a Forest Tent Caterpillar,
Malacosoma disstria.  According to BugGuide, there is:  “One generation per year; larvae spin silken mats on tree trunks and large branches where they congregate to molt or rest from feeding; larvae also deposit silk in strands along which they travel to and from feeding sites; overwinters as larva in masses surrounding tree branches. (Unlike Eastern Tent Caterpillar, this species does not form silken tents.)”

Letter 8 – Eastern Tent Caterpillar

what kinda Caterpillar is this?
Location: Lincoln, Alabama
April 16, 2011 5:41 pm
what kinda Caterpillar is this? found
4-16-11 in a bush!
Signature: what does that mean? my names hannah?

Eastern Tent Caterpillar

Dear Hannah,
This is an Eastern Tent Caterpillar,
Malacosoma americanum.  We located a nice web page on the biology of the Eastern Tent Caterpillar which includes this information about the tent:  “The tent of the eastern tent caterpillar is among the largest built by any tent caterpillar. The tents are constructed in the crotch of the host tree and are typically oriented so that the broadest face of the structure faces the southeast, taking advantage of the morning sun.  The caterpillars typically add silk to the structure at the onset of each of their daily activity periods.  Silk is added directly to the surface of the tent as the caterpillars walk back and forth over the surface of the structure.The silk is laid down under slight tension and it eventually contacts, causing the newly spun layer of silk to separate from the previously spun layer.  The tent thus consists of discrete layers separated by gaps within which the caterpillars rest.
The tent has openings that allow the caterpillars to enter and exit the structure.  Openings are formed where branches jut from the structure but are most common at the apex of the tent.  Light has a great effect on the caterpillars while they are spinning and they always spin the majority of their silk on the most illuminated face of the tent.  Indeed, if under laboratory conditions the dominant light source is directed at the tent from below, the caterpillars will build their tent upside down.  Caterpillars continue to expand their tent until they enter the last phase of their larval life.  The sixth-instar caterpillar conserves its silk for cocoon construction and adds nothing to the tent.
The tents appears multifunctional.  They facilitate basking, offer some protection from enemies, provide for secure purchase, and act as a staging site from which the caterpillars launch en masse forays to distant feeding sites. The elevated humidity inside the tent  may facilitate molting.”

Letter 9 – Caterpillar Pure

Reducing Bug Carnage
What a truly interesting site. I came here attempting to identify a critter I found in the house that I was unable to identify. Things like that worry me a bit now because my son lives in a group home that recently had to be fumigated for bed bugs. My wife was outraged that I would not allow him to spend overnight here while this task was undertaken. Her attitude quickly changed when I provided a mountain of information showing how insidious and infectious these creatures are and how easy it is to become infested with them. The bottom line was that within 30 seconds I had my sinister beast positively identified as a sow bug. I imagine you heard the sigh of relief all the way there. What blew me off my chair though is who you actually are.graphic designers. Is there no rock that remains unturned or mayhem we won’t commit in the name of creativity? I just roared until the tears ran down my cheeks. I think my pants need changing now too. Well done! I’ve been pretty creative too, but nothing like this. The only complaint I can lodge is that some of the pages are rather long, so it might be a good idea to insert a “back to top” link so that one does not have to scroll forever to get back to the other links at the top. It’s easy enough to do with some quick coding in simple HTML. After the first one it’s simple copy and paste in the coding until you go insane. Either that or you write a CSS style sheet that will do it automatically on every page.
And now, the real reason I’m emailing is to provide you with a very effective (although rather ugly) way of dealing with tent caterpillars and their ilk. This REALLY works, but it’s not for those who are squeamish. You’re not gonna like this…but it really works for these and other creepies like tent worms, army worms and cabbage worms. First of all you need to go to a garage sale and find a blender. You’ll get killed if you use the one in the kitchen for this. Collect a cup of the critters from your tree when they clump up in the tree for overnight warmth. Dump them in the blender and add 2 cups of water. Turn it to “puree” and leave it run for about 30 seconds. The water will turn green. Strain the resulting liquid through a coffee filter into a jar with a tight fitting lid. You’ll get about 2 cups of this delightful cocktail. It can be frozen for up to 6 months without any loss of potency. Mix at a ratio of 10 parts water to 1 part concentrate. Add a couple of drops of dish soap to make it stick to the leaves better. This can now be put in a sprayer and the afflicted plant sprayed. Aim at the leaves that are being eaten. Kills the worms dead and it won’t hurt anything else! Why does this work? Well, apparently they are not immune to their own gasto-intestinal gut bacteria and it is poisonous to them. Cheers!
Otter Brighteyes
www.members.shaw.ca/otterlimits/home.html
(This site addie will soon change as I have bought my own domain and private web space. The entire site is being rebuilt in proper XHTML Transitional. Does this matter?)

Dear Otter,
While we are happy to post your Pure

Letter 10 – Eastern Tent Caterpillar

We saw lots and lots of nests of these worms in the nooks of small trees at Bear Mountain NY. We didn’t notice them until the peaks which are around 1000 ft in altitude. They may have been at lower altitudes but we didn’t notice them there as much. Any idea what this insect is? We assumed it spins the nest so it’s maybe related to silk worms?
Ted

Hi Ted,
This is the tent of the Eastern Tent Caterpillar, Malacosoma americanum. The female lays eggs on tree branches in the fall and the egg overwinter, hatching in the spring. The caterpillars are social and spin the tent for protection.

Letter 11 – Forest Tent Caterpillar invasion in Canada

Subject: Caterpillar Infestation
Location: Regina, SK, Canada
July 4, 2014 11:04 am
I thought you might enjoy these pictures of a caterpillar infestation on tree trunks in Regina, SK, Canada. I was told by a local that they call these canker worms. There were about 10 trees all in a row and every tree trunk had these caterpillars on them in these large groups. Interestingly, I didn’t see a lot of foliage damage on the trees themselves, so I was wondering if they were somehow feeding on sap? The photos were taken in June. Thanks for your website. I love it.
Signature: Steven Sluder

Eastern Tent Caterpillars
Forest Tent Caterpillars

Hi Steven,
In May, we posted a letter with images from Maryland of a large aggregation of Eastern Tent Caterpillars,
Malacosoma americana, and they do feed on leaves.  According to BugGuide:  “larvae feed on leaves of many trees and shrubs but particularly members of the rose family such as apple, cherry, and crabapple.”

Correction:  April 16, 2016
These are actually closely related Forest Tent Caterpillars,
Malacosoma disstria, not Eastern Tent Caterpillars.  According to BugGuide, the caterpillars of the two species can be distinguished because “Eastern Tent Caterpillar (Malacosoma americanum) has an unbroken cream/white line along its back, and a dark face” while the caterpillar of the Forest Caterpillar is “dark-gray to brownish-black background body color, highlighted by broad, pale-blue lines and thin, broken yellow lines extending along each side; dorsum of each abdominal segment has distinct whitish keyhole or shoeprint-shaped marking; body has fine, whitish, and sparsely distributed hairs.”

Eastern Tent Caterpillars
Forest Tent Caterpillars
Eastern Tent Caterpillars
Forest Tent Caterpillars

Letter 12 – Forest Tent Caterpillar

What’s this teal caterpiller
I thought I sent this to you back in June but could find no answer. Found in Detroit area in June. Looked everywhere for a picture of it to no avail. Any idea?
Thanks, Chris

Hi Chris,
This is a Forest Tent Caterpillar, Malacosoma disstria. Although a gregarious feeder, this caterpillar does not form a tent. It is occasionally a pest, feeding on aspens, gums, maples, oaks, and many other forest and orchard trees. Caterpillar is found April to June. Here is a Florida site with information aplenty.

Letter 13 – Forest Tent Caterpillar

Subject: Help a Photographer out, please
Location: Toronto, Ontario, Canada
May 21, 2012 8:34 pm
Hello,
I’m a photographer and I love these two images I’ve attached. However, I have no idea what the insect is and would like to provide that information to clients potentially wanting to purchase prints.
It’s the same bug in both images.
Thanks for any help!
Signature: Adam Kerr

Forest Tent Caterpillar

Hi Adam,
These are photos of a Forest Tent Caterpillar,
Malacosoma disstria, a common species east of the Mississippi River.

Letter 14 – Forest Tent Caterpillar

Subject: Caterpillar identification
Location: Fort Worth, TX
April 18, 2015 3:19 pm
Hi –
Any chance that you can tell me what kind of caterpillar this is? I have two young girls that are very curious about it.
Signature: Not sure what this means…

Forest Tent Caterpillar
Forest Tent Caterpillar

Your caterpillar is a Forest Tent Caterpillar, Malacosoma disstria.

Letter 15 – Forest Tent Caterpillar

Subject: Bug Identity
Location: Palmer Tx
April 15, 2016 3:46 pm
These bugs are everywhere . I need to know what kind is it please?
Signature: Does not matter

Forest Tent Caterpillar
Forest Tent Caterpillar

This is a Forest Tent Caterpillar, Malacosoma disstria, a social species that often feeds in large groups.  Periodically, there are significant population explosions, and based on this submission of Forest Tent Caterpillars we received last week, this is one of those years in Texas.

Letter 16 – Forest Tent Caterpillar

Subject: Brown striped caterpiller
Location: SW Ohio
May 9, 2016 6:48 am
I live near Dayton, OH, and found this caterpiller on my patio table. I have never seen one like this. Can you help ID it?
Thank you.
Signature: Jennifer

Forest Tent Caterpillar
Forest Tent Caterpillar

Dear Jennifer,
This distinctive caterpillar is a Forest Tent Caterpillar,
Malacosoma disstria.  According to BugGuide:  “larvae feed on leaves of alder, basswood, birch, cherry, oak, poplar, willow.”

Letter 17 – Forest Tent Caterpillar Moth

Subject: I love this website.
Location: Ashland, Oregon
February 17, 2014 7:53 am
Hello again, Daniel! I hope this letter finds you well. 🙂 I was just going through some old photos from last summer in Oregon and wanted to share them with you (a wooly moth, ants on a peony flower, and a yellow jacket in my cabin. ) I think I have the last two photos identified correctly, but just wanted to include them because I like the photos. The first one, however, I’m not really sure about. I love this little guy though, in my mind he looks like a sweet little sheep or maybe a strange new Star Wars character.
Signature: Rachel

Forest Tent Caterpillar Moth
Forest Tent Caterpillar Moth

Hi again Rachel,
We believe we have correctly identified your yellow moth as a Forest Tent Caterpillar Moth,
Malacosoma disstria, and it took far less time than we anticipated.  The first matching photo we found was on the Wanderin Weeta blog, but alas, the moth is not identified.  We then turned to BugGuide and guessed correctly with the Lappet Moth and Tent Caterpillar family Lasiocampidae.  We were searching for an image shot at the same angle as yours, and this female Forest Tent Caterpillar Moth on BugGuide looks like a good match, except for the antennae, but male moths have more developed antennae so they can locate the female through her pheromones.  This image of a male Forest Tent Caterpillar Moth on BugGuide has antennae like your individual.  According to BugGuide:  “larvae feed on leaves of alder, basswood, birch, cherry, oak, poplar, willow.”  

Letter 18 – Forest Tent Caterpillars

Subject: Under the motorhome
Location: East Texas
April 4, 2015 6:31 pm
We just spent the past five months in an RV park near Miami FL. On the way home to CA, we stopped in Livingston TX. We were here for a week when this afternoon I found this infestation of caterpillars around the front of the RV and no where else in the area.
My questions:
What are they?
Did I bring them from FL to TX?
Is this a problem?
Signature: Frank Liberty

Forest Tent Caterpillars
Forest Tent Caterpillars

Dear Frank,
These are Forest Tent Caterpillars,
Malacosoma disstria, which we quickly identified on BugGuide, and while we cannot say for certain that you did not transport them from Florida to Texas, we believe it is highly unlikely.  According to BugGuide, they are found in both Florida and Texas, and they can be distinguished from other Tent Caterpillars based on this BugGuide description:  “Larvae: dark-gray to brownish-black background body color, highlighted by broad, pale-blue lines and thin, broken yellow lines extending along each side; dorsum of each abdominal segment has distinct whitish keyhole or shoeprint-shaped marking; body has fine, whitish, and sparsely distributed hairs.”

Letter 19 – Mexican Tent Caterpillar

Hello again from the Yucatan of Mexico
You helped me with a lovely (and pesky) melon moth a month or so ago and now I have a new question. The attached photos show a woolly caterpillar that has a hard and shiny reddish head. One photo shows how they gather at the base of trees during the daytime. At night they climb the local trees – one they seem to like a lot is a wild fig – and eat the leaves until they look like lacework. Then, as the sun comes up they stream down the tree trunks to gather in hollows and under logs. They are really doing a number on the trees and if they are going to hatch into something noxious I may consider spraying them to reduce their numbers near the area where we live. We live in a dense jungle so won’t be anything close to eliminating them overall. Another characteristic is that they sometimes have a spiderweb-like thread that they emit. I googled the description but don’t find anything. I have looked at all of you photos and don’t see one that looks quite like it nor any description of the behavior. Can you help?
Kathe Kirkbride

Hi Kathe,
Your written description and photos indicate this is probably some type of Tent Caterpillar, though many do not form tents. Huge aggregations often do considerable damage, but these large numbers are cyclical and do not occur every year. Loosing leaves is not a life threatening situation for trees. Poison might do more harm than good.

Letter 20 – Possibly Tent Caterpillar Nest or Fall Webworm Nest

Subject: Nest
Location: Southwestern Pennsylvania 18mi north of Pittsburgh
May 19, 2013 10:17 pm
Today I photographed and interesting cocoon like nest, with a bunch of something(maybe insects) inside.
I’ve never seen a nest like this in the trees. It may, for all I know, it may be a small, tent caterpillar’s nest.
But the ones I’ve always seen are much larger.
I didn’t dig into the nest to find out ’cause I didn’t want to intrude on the bugs. Any Ideas?
Signature: Rich

Nest might belong to Tent Caterpillars
Nest might belong to Tent Caterpillars

Dear Rich,
We agree with you that this might be the newly started nest of a recently hatched colony of Eastern Tent Caterpillars.  We will try to get a second opinion from Eric Eaton.  More information on the Eastern Tent Caterpillar can be found on BugGuide.  As an aside, we will be flying into Pittsburgh in a few weeks to visit family.

Possibly Tent Caterpillar Nest
Possibly Tent Caterpillar Nest

Eric Eaton provides another possibility
Daniel:
Tough call.  I’m thinking Fall Webworm, as they tend to make webs on the outer reaches of branches, whereas tent caterpillars build webs in the crotches of branches, often several “tents” to one tree, or in a series of trees close to each other.  Fall Webworm tends to have more isolated colonies.
Eric

Thank you so much for the return email.
Have a good trip and a great stay at, “Da Burgh”.
Thank you both again for the rapid response and ID.
Isn’t it a bit early for webber caterpillars to appear?
Richard Rich

Once we received Eric’s response, we pondered the time of year.  Tent Caterpillars already have established nests in the spring and Fall Webworms are most noticeable later in the season, but they do begin hatching earlier.  Your “nest” might be the beginning of what will become a substantial “web” later this year.

Letter 21 – Tent Caterpillar Moth

Tent Caterpillar Moth
Tent Caterpillar Moth

Subject: Moth
Location: Northwestern NM
October 8, 2014 11:05 am
Saw a lot of these at a gas station, folded like little tents until I rousted one for a picture.
Signature: Brent

Hi Brent,
In our opinion, this looks like one of the Tent Caterpillar Moths in the genus
Malacosoma, and there are several species pictured on BugGuide.  The only doubt is that BugGuide indicates:  “adults in late spring and early summer.”

Letter 22 – Tent Caterpillars

rockin’ caterpillars
These little fellows were twitching in their mass cocoon. The picture was taken in early summer. Can you identify them?
Mike
Boise, ID

Hi Mike,
These are Tent Caterpillars, probably Eastern Tent Caterpillar, Malacosoma americanum. Here is a link with additional information.

Letter 23 – Tent Caterpillars

Tent caterpillars
and a closeup….This was taken near a child’s park in Asbury, NJ on Mother’s Day 2007. I found this about them on Wiki “Tent caterpillars are moderately sized caterpillars in the genus Malacosoma in the moth family Lasiocampidae. Species occur in North America, Mexico, and Eurasia. Twenty-six species have been described, six of which occur in North America. Some species are considered to have subspecies as well. Although most people consider tent caterpillars only as pests due to their habit of defoliating trees, they are among the most social of all caterpillars and exhibit many noteworthy behaviors. Tent caterpillars are readily recognized because they are social, colorful, day active and build conspicuous silk tents in the branches of host trees. Some species, such as the eastern tent caterpillar, Malacosoma americanum, build a single large tent which is typically occupied through the whole of the larval stage while others build a series of small tents that are sequentially abandoned. The forest tent caterpillar, Malacosoma disstria, is exceptional in that the larvae build no tent at all, aggregating instead on silken mats that they spin on the leaves or bark of trees. Tents facilitate aggregation and serve as focal sites of thermal regulatory behavior. They also serve as communication centers where caterpillars are alerted to the discovery of new food finds, as discussed below.”
Debbie

Hi Debbie,
Thanks for sending us your photos and providing the factual information.

Letter 24 – Tent Caterpillars

A moth or butterfly?
June 8, 2010
Dear fellow bug people:
I’ve been trying to grow a butterfly garden so that I may start one in our school next year. I teach first grade and the students love them. I walked into my back yard and found about 9 groups of these little guys on a tree I did not plant (go figure!). Anyway I believe they are moth caterpillars. It would be nice to know more. I would love to know what they are and if I can bring some into the classroom without my lil people getting hurt. I could not get a closer picture without ‘bugging’ them 🙂 Hope you can help me!
Saymith Morales – First Grade Teacher
Enterprise, Alabama

Tent Caterpillars

Dear Saymith,
Though your photo is quite blurry and lacking in detail, we have little doubt that this is these are Eastern Tent Caterpillars, Malacosoma americanum.  They are moth caterpillars, and they could easily be brought into the classroom for your first grade students to learn about metamorphosis, but we think other species might be more appropriate.  BugGuide provides information on the species, but directs viewers to another website for details about the life cycle.  Adult moths are a drab brown, and they are not the most dramatic conclusion to metamorphosis, but they will still provide a valuable learning experience.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

11 thoughts on “Forest Tent Caterpillar: All You Need to Know in a Nutshell”

  1. i have found these around where i live there is a tree around the corner from me with all these silk nest (maybe 20) will they become butterflies?

    Reply
  2. Thank you so much! I’m on my phone, and the mobile site won’t let me post a pic update, so I’ll send a separate pic. Thank you again!

    Reply
  3. Thanks for the pics!
    I’ve had a recent invasion (though not as massive as yours!!) of caterpillars in my yard and this post was exactly what I needed to identify them! It helps that you’re in the neighborhood (I’m in Baltimore city). My yard backs up against some woods, so I guess they’ve been coming out to eat my cauliflower and Brussels sprout plants as well as some other plants in my yard. It’s useful to know they’re not a butterfly!

    Reply
    • Tent Caterpillars will not eat your cauliflower or Brussels sprouts. They do feed on the leaves of a variety of trees, especially, according to BugGuide, “members of the rose family such as apple, cherry, and crabapple”

      Reply
  4. Thanks for the pics!
    I’ve had a recent invasion (though not as massive as yours!!) of caterpillars in my yard and this post was exactly what I needed to identify them! It helps that you’re in the neighborhood (I’m in Baltimore city). My yard backs up against some woods, so I guess they’ve been coming out to eat my cauliflower and Brussels sprout plants as well as some other plants in my yard. It’s useful to know they’re not a butterfly!

    Reply
  5. Yah they sure are quit the bug. Army cartipilar is what we called them. I’m in Moose jaw Sask now, but that was quit a while ago when I lived in North bay Ontario Canada and I was trying to remember the exact year but I can’t. I was wondering if you could tell me the year that we had that infestation Please and Thank-you Karen

    Reply

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