Bagworms are caterpillar pests known for the unique protective cases they construct around themselves.
These cases, often referred to as “bags,” are made using silk and materials from the plants they feed on.
At a glance, these bags can resemble small pinecones or clusters of pine needles, making them easily mistaken for natural parts of the trees or shrubs they inhabit.
Inside these bags, one might find the developing larvae, eggs, or even the adult female bagworms preparing for the next generation.
As the larval form of the bagworm moth, these creatures play a significant role in their life cycle, transitioning from feeding larvae to reproductive adults.
In this article, let’s understand where these bagworms come from and how they can be a pest in your garden and home.
What Are Bagworms?
Bagworms are the larval stage of the bagworm moth, a species that has evolved a unique method of protection during its developmental phase
These larvae create and reside within bags, which serve both as a shield against predators and as a means of camouflage within their environment.
These bags are meticulously crafted using silk produced by the larvae, combined with bits of leaves, needles, and other plant materials from their host plants.
While the term “bagworm” might suggest a worm-like creature, it’s essential to understand that these are, in fact, caterpillars.
As they mature, they undergo a transformation within these bags.
Male bagworms eventually metamorphose into winged moths, leaving their bags to seek out females for mating.
In contrast, female bagworms remain wingless and largely resemble their larval form throughout their lives.
They stay within their bags, laying their eggs inside, which will hatch into the next generation of bagworms.
Where Do Bagworms Come From? Origin and Distribution
Bagworms, particularly the North American bagworm, have a widespread presence throughout the continental U.S. and southern Canada.
This species has counterparts that extend their range into Central and South America, reaching as far south as Argentina.
Where Do Plaster Bagworms Come From? – Origin and Distinguishing Features
Plaster bagworms are a species of moth known as Phereoeca Uterella. Their larvae form casings, which they live inside during their vulnerable period.
These casings are around half an inch in length and feature slits at both ends, allowing the larvae to move in and out.
The most distinguishing characteristic of plaster bagworms is their bag, which looks like a small cocoon.
This bag, resembling a watermelon or pumpkin seed in shape, is made up of silk fiber and other organic materials, such as lint, sand, or dry plaster debris.
The cocoon’s color is light gray and hangs discreetly on walls. Inside this protective casing, the larva, primarily white with a brown head, resides.
These pests are especially prevalent in humid environments, such as the Southeastern United States, with a significant presence in Florida.
Bagworm Life Cycle
Bagworms begin their life cycle with eggs laid by the female inside the protective bag.
This bag serves as a safeguard, shielding the eggs from cold temperatures throughout the late fall and winter months.
Depending on the location, these eggs typically hatch in the spring to early summer.
After hatching, the young caterpillars venture out to feed on the needles and leaves of their host tree.
Contrary to what one might assume, bagworms are not stationary creatures.
Young worms can transport their bags with them, moving around in search of food.
This mobility allows them to feed on various parts of the host plant, causing potential defoliation and other damage.
As the seasons progress, bagworms transition into the pupal stage by fall. During this phase, they transform into adults.
Female adults, being wingless, remain in their bags, while males leave their bags to locate females for mating.
Post-mating, the female lays over 300 eggs inside her bag, which will endure the winter and hatch the following spring, completing the life cycle.
Habitats and Host Plants
Bagworms have a preference for certain trees and plants, which serve as their primary habitats.
These insects are known to reside in a variety of trees such as willow, spruce, maple, oak, and pine.
Among these, arborvitae and juniper trees are their favorites. However, bagworms are adaptable creatures.
In the absence of their preferred trees, they can settle in decorative shrubs that provide a suitable food source.
Do Bagworms Come From the Ground?
A common misconception is that bagworms originate from the ground. In reality, bagworms do not come from the soil.
Instead, they begin their life cycle in the protective bags, usually attached to host trees or plants.
These bags shield the eggs during the colder months, and once hatched, the larvae feed on the foliage of their host plant.
The bags can sometimes be found on the exteriors of structures or other locations, but this is typically the result of caterpillars moving their bags to pupate rather than an indication of ground origin.
Signs of Bagworm Presence in Residential Areas
One of the most evident signs of bagworm presence in residential areas is the distinctive bag they create.
These bags can be easily spotted hanging from tree branches or leaves.
At first glance, a bagworm’s bag might resemble a small pine cone or a collection of pine needles stuck together.
When freshly constructed, these bags can range in color from green to light brown.
However, as they age, especially throughout the winter months, they fade to a grayish-brown hue.
If you notice a tree or shrub appearing as though it’s losing its foliage, it’s essential to inspect it closely to determine if bagworms are the cause.
Why Certain Trees and Bushes Are More Susceptible
Bagworms are not random in their choice of habitat. They specifically look for places that can also serve as food sources for themselves and their offspring.
While they can survive on a variety of trees, they have a particular preference for conifers.
The reason for this preference is that conifers do not produce a new crop of foliage every year, making them more vulnerable to the damage caused by bagworms.
Trees like evergreens, which retain their leaves or needles throughout the winter, are at a higher risk of severe damage or even death due to defoliation by bagworms.
On the other hand, deciduous trees can often survive a bagworm infestation, but it’s always better to address the issue before it escalates.
How Do You Prevent Bagworms?
Preventing bagworms involves a combination of regular monitoring, physical removal, and, if necessary, the use of specific treatments. Here are some steps to prevent bagworm infestations:
- Regular Inspection: Regularly inspect trees and shrubs, especially those known to be preferred by bagworms such as juniper, arborvitae, spruce, and pine. Early detection is crucial to managing and preventing a full-blown infestation.
- Physical Removal: If you spot bagworm bags on your trees or shrubs, especially during the winter months, physically remove them. This is effective because each bag can contain hundreds of eggs that will hatch the following spring. Use scissors or shears to snip off the bags and place them in a bucket of soapy water to kill the larvae, or seal them in a plastic bag and dispose of them.
- Biological Control: Introduce natural predators like birds and beneficial insects that feed on bagworms. For instance, certain parasitic wasps can help control bagworm populations.
- Biorational Insecticides: If you detect an infestation early, typically in May or June, you can use biorational insecticides like Bt (Bacillus thuringiensis), neem, or Spinosad. These are especially effective on younger bagworms.
- Chemical Control: For more severe infestations or when bagworms are discovered later in the season, consider using synthetic insecticides like bifenthrin, sevin or carbaryl. However, always use chemical controls as a last resort and follow label directions carefully. It’s also essential to note that while these insecticides can reduce the number of bagworms, they might not eliminate the population entirely.
- Maintain Tree Health: Healthy trees are more resilient to pests, including bagworms. Ensure your trees are well-watered, appropriately pruned, and receive the necessary nutrients.
- Consult with Experts: If you’re unsure about the presence or severity of a bagworm infestation, consult with a local extension service or a professional arborist. They can provide guidance tailored to your specific situation.
- Educate and Collaborate: Share information about bagworm prevention with neighbors. Collaborative efforts can be more effective in preventing the spread of bagworms across a larger area.
Remember, the key to preventing bagworms is early detection and intervention. Regularly inspecting your trees and shrubs and taking prompt action can help keep these pests at bay.
Health and Environmental Implications
Bagworms, despite their potential to cause significant damage to trees and shrubs, are not harmful to humans or animals.
If you happen to come into contact with a bagworm or its bag, there’s no cause for concern; they won’t harm you or cause any sickness.
However, it’s essential to note that while the bagworms themselves are harmless, the pesticides often used to treat bagworm-infested trees can be toxic.
These pesticides can pose risks to humans, animals, and even beneficial insects if not used correctly.
Therefore, while addressing a bagworm infestation, it’s crucial to be cautious and informed about the chemicals being used.
Frequently Asked Questions
How harmful are bagworms?
Bagworms are harmful primarily to trees and shrubs, causing defoliation which can lead to plant death, especially in evergreens. It’s advisable to manage bagworms to protect your plants. To get rid of bagworms, physically remove their bags from plants, drown them in soapy water, or use specific insecticides, ensuring early detection for effective control.
Should I kill bagworms?
Yes, if bagworms are infesting your plants, it’s advisable to manage and control them. Left unchecked, they can cause significant defoliation and potentially kill plants, especially evergreens. Early intervention can prevent extensive damage to your landscape.
How do I get rid of bagworms?
To get rid of bagworms, manually remove the bags from trees and drown them in soapy water. If infestations are caught early, use biorational insecticides like Bt (Bacillus thuringiensis), neem, or Spinosad. For older bagworms, synthetic insecticides like bifenthrin or carbaryl may be effective. Always consult with a pest control expert for severe infestations and follow label directions for any pesticide.
Bagworms, the larval form of the bagworm moth, are fascinating creatures with a unique life cycle.
Originating primarily from North America, they have spread to various parts of the world, with their distinctive bags serving as a protective home during their larval stage.
These bags, made from silk and materials from their host plants, are a clear sign of their presence in residential areas.
While they prefer certain trees, especially conifers, they are adaptable and can infest a range of trees and shrubs.
Though harmless to humans and animals, their potential to damage trees makes it essential to manage and control their populations effectively.
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 – Bagworm from South Africa
My dad just sent me this photo, he lives is Johannburg, south africa. We have never seen anything like it. Could it be the bagworm?
We agree that this is a Bagworm.
Letter 2 – Bagworm Moth from New Zealand
Subject: Found a pair of these, metallic blue with orange and black Location: New Zealand March 12, 2013 6:57 pm Hi we found two of these on our deck, it’s summer over here at the moment. The bug looks like a form of ladybug with black and orange wings, and possibly a set of metallic blue wings over the top? The antenna has white tips, and the legs look black, The abdomen is the part that makes me think it’s not a ladybug…. We have never seen one before, and wondering what they are Thanks heaps Signature: Gizmo_RA2 Dear Gizmo_RA2, We believe this is a moth and that its wings haven’t fully expanded, but we have been unable to find a matching image online. Perhaps one of our readers will have better luck than we had. Chad provides an identification: Bagworm Moth Chad provided this link to a Bagworm Moth, Cebysa leucotelus. According to the Landcare Research Manaaki Whenua website: “Caterpillar forms an untidy bag to live in Found on rock walls and houses. Feeds on minute algae and lichen Adult female is often mistaken for a beetle. Adult female can fly, but only in short hops Male is fully winged”
Letter 3 – Flightless Bagworm Moth from New Zealand
Subject: “Australian” Bagworm Moth Location: Epsom, Auckland March 14, 2014 2:54 pm Never seen one before but I spotted and I think correctly identified an Australian Bag Moth yesterday 14 March 2014 in Epsom, Auckland Signature: Lindsay Dear Lindsay, Thanks for submitting your photo of a flightless, female Bagworm Moth, Cebysa leucotelus. According to Nature Watch: “It is found in New Zealand and the southern half of Australia (Tasmania, Victoria and Western Australia). The adult female moth has black wings with yellow wingtips and patches, but they do not expand properly, so she is not able to fly. The male has a similar pattern and colouring, but has no iridescence. His wings are fully developed and adult males can fly normally. The larvae feed on lichen.”
Letter 4 – Flightless Female Bagworm Moth from Australia
Subject: BUG Location: SYDNEY AUSTRALIA October 19, 2013 2:11 pm I PHOTOGRAPHED THIS INSECT IN MY BACKYARD LAST SUMMER. CAN YOU PLEASE IDENTIFY THIS STRANGE AND BEAUTIFUL INSECT. I HAVE SEARCHED MANY SITES WITH NO RESULTS. ITS ONLY SMALL NO MORE THEN 2CM HAS SMALL COLORFUL WINGS AND APPEARS FLIGHTLESS ONLY CRAWLS AND HOPS. I HOPE YOU RECEIVE MY FILES Signature: WHAT BUG IS IT This is a flightless female Bagworm Moth, Cebysa leucotelus. Your photos are excellent. You can find additional information on Butterfly House. We will be postdating your submission to go live in early November while we are out of the office.
Letter 5 – Bagworm from the Philippines
Subject: What kind of bug is this? Location: Cebu, Philippines July 17, 2015 6:01 am I don’t know what this bug is and I’m dying to find out. My curiosity is killing me. It’s a very tiny bug supporting a huge shell of some kind of wood shavings , if you will. Hoping for an answer!! Signature: What This is a Bagworm, the caterpillar of a moth in the family Psychidae. Bagworms construct shelters from bits of plant that act as camouflage as well as protection.
Letter 6 – Bagworm from Singapore
Subject: Bug Location: Singapore August 24, 2012 1:07 am Dear Sir, I live in Singapore, and I found this but that look as carry pieces of wood on his back the size is +- 2-3cm crawling on the wall but have king of string connect as a spider. I gave him a name Xpus just sound cool 🙂 thanks in advance. Frank Signature: Bug Hi Frank, This is a Bagworm in the family Psychidae. We located an Ecological Observations in Singapore Blog posting of Bagworms that has one image that somewhat resembles the head of your Bagworm. We cannot be sure they are the same species. Bagworms construct their bags from pieces of the plants they feed upon. The bags act as camouflage and protection.
Letter 7 – Flightless Female Bagworm Moth from Australia
What’s this funny insect? Location: Sydney, Australia April 13, 2011 7:03 am This creature was on the wall the other day. I have never seen anything like it. Any idea what it is? Is it dangerous? The spike on the back looks a bit scary! Signature: Carey Dear Carey, Just a few days ago, we had another identification request for this flightless female moth from Australia, and it was identified as a Bagworm Moth, Cebysa leucotelus. Only the females are flightless. We suspect that is an ovipositor protruding from her abdomen. Dear Daniel, Thank you for that! I hope she laid her eggs outside first. Carey
Letter 8 – Bagworm from Greece
Subject: Bug that carries its home with it Geographic location of the bug: Larisa, Greece Date: 04/04/2018 Time: 07:56 AM EDT Your letter to the bugman: I find this one bug occasionally in my garden and I believe its always the same one I see (I’ve never spotted two or more together). It doesn’t seem harmful but I’m scared to touch it and I don’t want to bother it. It always carries something on its back as you can see in the photo. Sometimes I find it immobile with it being entirely inside the thing on its back. It has six legs from what I can see. I’d really like to identify it. How you want your letter signed: EntomologistWannaBe Dear EntomologistWannaBe, This is a Bagworm, the caterpillar of a moth in the family Psychidae. We located a beautiful poster on Etsy with images of the Hairy Sweep, Canephora unicolor/Canephora hirsuta, which is described as “a moth of the family Psychidae. It is found in Europe. The female has no wings. The wingspan of the male is 20–25 mm. The moth flies in one generation from May to July. The larvae feed on shrubs, deciduous trees and herbaceous plants.” There are also images on Papillon en Macro, Project Noah and BioLib. Bagworms construct a bag from bits of plants that they drag around and use for protection, eventually pupating inside the bag.
Letter 9 – Mystery Caterpillar from Costa Rica similar to Bagworm
mysterious large cocoon with a caterpillar inside. April 5, 2010 I found him on the ground in my yard in Costa Rica. I brought it inside to hatch, but he just comes partially out to eat and poops round pellets out of the bottom, and spends most of his time inside. I have had him for about 5 days now. He has moved about to different locations, until i found a place he likes with leaves he likes to eat. He attached himself to a branch i provided with a small silk thread, and has remained there. Is it normal for a caterpillar to continue to eat after spinning a cocoon, or is this his protective living space? Will it eventually pupate? Jan Betts Costa Rica, Central America 3000 feet altitude.