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Gypsy Moth Caterpillar Identification
Gypsy moths are an invasive species that can destroy entire forests. It is critically important to control their spread. If you have found caterpillars that you think might be gypsy moths, this identification guide can help.
The photos in this guide show you exactly what these destructive caterpillars look like. Gypsy moth caterpillars have a very distinctive and consistent pattern consisting of red and blue raised bumps. It only takes a little close-up examining to tell if the caterpillar you have found is indeed the destructive gypsy moth. Let's start by going over some basics.
Gypsy moths get their name from their ability to travel long distances and show up far from home. The egg masses are often transported by firewood, building materials, or even car tires.
Lymantria dispar is composed of two Latin-derived words. Lymantria means "destroyer," and dispar is derived from the Latin for "unequal," referring to the differing characteristics between the adult male and female gypsy moths.
Males are brown and fly during the day, like butterflies; females are cream and black and don't fly far, or at all, from where they hatch out from the cocoon. Males come to to them as they sit where they have hatched out, and they lay eggs in that same spot.
Gypsy moths can be found throughout much of the world. The gypsy moth was introduced into North America in 1869 from Europe, and quickly became one of the country's first, and worst, destructive invasive species.
Mature Gypsy Moth Caterpillar Identification
There are several unique features that identify this species, but there is one absolutely surefire way to tell if your caterpillar is a gypsy moth. Gypsy moth caterpillars have a very distinctive pattern of raised bumps that no other caterpillar has. Look for two rows of blue bumps in the front and two rows of red bumps in the back. If the caterpillar you have found has this pattern of raised, spiny bumps, then there is no question that you found a gypsy moth caterpillar.
Did You Find a Gypsy Moth Caterpillar?
Immature or Baby Gypsy Moth Caterpillar Identification
Immature gypsy moth caterpillars are a little more difficult to identify, but they have one distinguishing characteristic that you can use. Immature gypsy moth caterpillars have two furry bumps, one on either side of their head, that give them the appearance of having a "collar." If you have found a caterpillar that is tiny, furry, and has noticeable collar-like lumps on either side of the head, then you very likely have found a gypsy moth caterpillar. Look around—there are probably many more!
Baby Gypsy Moth Caterpillars Often Dangle From a Thread
This behavior is shared by many other caterpillars, so this identifying factor alone does not mean you have gypsy moths. However, immature gypsy moth caterpillars have been known to descend from their food plant on a silk thread and hang there for a bit. This may be to escape a predator like an ant or a beetle, but more likely it's due to a particular method these caterpillars have for spreading to new territory.
The baby caterpillars are so light and furry that a good breeze can carry them for long distances—sometimes even for many miles. One study suggested that immature gypsy moth caterpillars used this method to spread all the way across Lake Michigan—a distance of 50 miles—during a storm!
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Gypsy Moth Caterpillars Almost Always Occur in Groups
It's very unusual to have only one gypsy moth caterpillar on your trees. They typically show up in large numbers, and even if you have found only one, a little looking will turn up many more. For every one that you can find, there are dozens or even hundreds more up in your trees, eating and growing.
The Spread of the Gypsy Moth Caterpillar in the USA Over Time
What do Gypsy Moths Eat?
The answer to this is "almost everything." If it has leaves, the gypsy moth will use it as a host plant. That said, there are several species that the gypsy moth is notorious for attacking, and many of them are mainstays in forests around the world.
Trees that are most often attacked by gypsy moth caterpillars include alder, apple, aspen, beech, birch, boxelder, crabapple, hawthorn, hazelnut, larch, linden, mountain ash, and just about every kind of oak, their favorite food.
Gypsy Moth Rashes
Some people are very sensitive to the stiff hairs on gypsy moth caterpillars. For some, the reaction is as bad a poison ivy, which produces itchy blisters that can persist for weeks. Most people, however, do not have this reaction, even though a prickly dermatitis can result in contact with the caterpillars. Other species, like the brown tail moth, are similar in appearance but are legitimately venomous and can create a dangerous allergic reaction in some people.
What to Do if You Think You Have Gypsy Moth Caterpillars
The first thing to do is to get on the phone and contact your state's Department of Agriculture! Gypsy moths can be a serious threat to forests and green spaces—not just your backyard garden. If you report these pests, you may be helping to save your town's parks. Here are some local methods of control, courtesy of planetnatural.com.
How to Get Rid of Gypsy Moth Caterpillars
- Set up a gypsy moth trap that can be used to monitor the moth population and prevent male moths from homing in on females.
- A sticky trap like the Tanglefoot Pest Barrier can be placed around tree trunks to stop caterpillars from traveling up to where the leaves are.
- Azadirachtin, the key insecticidal ingredient found in neem oil, may help repel gypsy moths.
- Diatomaceous earth is a non-toxic, naturally occurring substance that controls caterpillars of all kinds. Use very sparingly to avoid killing all of the good insects in your yard or garden!
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Liz Westwood from UK on June 17, 2020:
This is an extremely well-illustrated, interesting and informative article. I have learnt a lot about Gypsy moths from reading it.
Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on June 17, 2020:
GreenMind, I start to learn all this when I was a boy. But here I am refining my knowledge and understanding. Thanks for sharing.