Are Caterpillars Poisonous to Dogs? (+ Can They Eat Them Safely)

are caterpillars toxic to dogs

Caterpillar season usually means one of two things to dog owners; firstly, it won’t be long before your dog is chasing beautiful butterflies, or secondly, it’s that time of year where your dog tries to actually eat the caterpillars.

Dogs are naturally curious creatures, and given how slowly caterpillars can move, it’s no surprise if your pet comes into contact with them. They can brush up against plants, lick one, or even eat them.

But are caterpillars poisonous to dogs? What would happen if your dog ate one? Will they get sick, or even die?

I decided to research into what the reality of caterpillar toxicity is for dogs in Australia, Canada, the UK, and the United States. It makes for surprising reading and if you scroll near the bottom of the page you can see a list of the most poisonous caterpillars to dogs.

But firstly, here’s the short answer…

Are caterpillars poisonous to dogs? Some caterpillars are poisonous to dogs. Depending on the caterpillar type, some will ingest toxic weeds that can make a dog sick, other caterpillars have poisonous spines and stinging hairs that can harm your dog too. But most are actually harmless to dogs.

As a pet owner myself, I don’t let my dog near caterpillars. I do this to be completely on the safe side. But I don’t want to overly alarm you, not all caterpillars are toxic to dogs, only some – and here’s why.

Why some caterpillars can harm dogs

Depending on where you are in the world and the type of caterpillar you’re faced with determines the danger… and you can see a list of the most dangerous ones lower down the page.

Here’s why some can make your dog ill:

  • Some innocuous caterpillars eat weeds that are toxic to dogs. When the dog then eats the caterpillar, the toxicity gets into their system, being potentially fatal.
  • Other exotic caterpillars have poisonous spines and hairs on their body which are designed to ward off predators. These can also prove fatal to dogs. In most cases though will give a string, create irritation and possibly be allergy inducing.
  • Even a non-toxic caterpillar could harm a dog if eaten. It could disagree with your dog’s digestive system or result in an allergic reaction.
  • Some caterpillars might even have parasitic worms in them which could transfer to your dog – I explained a similar issue in my guide to dogs eating slugs.

In terms of country by country analysis, here’s what you should look out for:

  • United Kingdom: There didn’t use to be any toxic caterpillars in the UK until recent years. The UK government has recently issue a warning about the dangers to dogs from non-native caterpillar species that are now on the British Isles.
  • United States & Canada: North America has caterpillars that not only feed on milkweed, making them toxic to dogs when ingested, but also have a range of different harmful ones native throughout the entire continent.
  • Australia & New Zealand: One of the most dangerous caterpillars to canines lives in Australia. Both countries can also have toxic caterpillars infused with the ragwort plant – which is poisonous to dogs.

What does this mean for you as an owner?

Well, unless you have an encyclopaedic knowledge of caterpillars, I would avoid them completely.

If you do want to know your caterpillars though, here are some of the most common varieties and how dangerous they could be.

Are Woolly Bear caterpillars poisonous to dogs?

Whilst Woolly Bear caterpillars look highly toxic due to their coloration, they aren’t actually poisonous to dogs. However, they can hurt your dog for another reason.

woolly bear
The Woolly Bear caterpillar – copyright M L Rieser on Wikipedia.

This variety has very bristly hair. It’s not venomous but if your dog eats a Woolly Bear caterpillar, the hair can get stuck in their throat. This can lead to a possible allergy, but most likely coughing, gagging, and retching.

Are tent caterpillars poisonous to dogs?

Tent caterpillars seem to be on the increase. However, as far as I can tell from my research, they do not bite or sting, and so should not be poisonous to dogs.

But they could hurt your dog’s insides with the spiky hairs if eaten and could even possibly be carrying a parasite. So, you might ask, can dogs eat tent caterpillars? I would say it might ok, but it’s not recommended.

However, you should exercise caution if you own horses. According to NJ.com:

“Tent caterpillars have a history of causing spontaneous abortions in horses in Kentucky. Horses were eating the caterpillars and their spiny hairs were piercing the horse’s stomachs, causing a bacterial infection and miscarriages in pregnant mares.”

Other common caterpillars

I also discovered some other caterpillars that dog owners frequently ask about.

  • Green caterpillars: How poisonous they are is dependent on the variety. Some green ones are harmless, but other will be toxic. Keep scrolling for the most poisonous to look out for.
  • Fuzzy caterpillars: I would be more wary of fuzzy caterpillars as this is usually a sign that they have either poisonous spikes, or sharp hairs that can get stuck in your dog’s skin or throat.
  • Oleander caterpillars: Caterpillars that feed on the oleander leaves can be toxic. Oleander contains Cardiac Glycosides which are poisonous to dogs and people.
  • White caterpillars: As with other varieties, it depends on the breed.

Why do dogs eat caterpillars?

Dogs can eat caterpillars if you’re not careful.

But why do they do it in the first place? You wouldn’t think they would look appetizing to dogs? However, there are some good reasons why your dog might eat them…

Why do dogs eat caterpillars? Dogs eat caterpillars often my accident, for example when eating another food with a caterpillar on. Other times it can through pure curiosity.

What happens when a dog eats a caterpillar?

Dogs can get sick from eating caterpillars, but the nature of their illness will vary depending on the caterpillar type.

If they eat a caterpillar that has been feasting on milkweed or ragwort, they can quickly become poisoned. This weed is toxic to your dog’s heart and can be fatal if not treated.

When dogs eat caterpillars with poisonous spines, they can go into shock, or suffer intestinal problems. Other caterpillar body hairs can cause irritation.

The bottom line is, if you see any change in behavior, talk to your vet. In fact, if you even have the slightest suspicion your dog ate a caterpillar, call your vet for advice.

The 17 most dangerous caterpillars in the world

In no particular order, here’s a list of some very dangerous caterpillars that could either hurt or fatally wound your dog – some could even kill you too!

1. American Dagger

As the name suggests, this caterpillar is native to North America. It has long black spikes, that whilst not poisonous enough to kill a dog, can leave a nasty sting.

dagger moth
The spiky America Dagger moth caterpillar – image copyright Wikipedia.

If you have these in your garden, get a pair of gloves on before you even go near them as the sting can leave an itchy burn that often develops into a rash. Imagine how that would feel if your dog ate one of these caterpillars or got one near their mouth.

2. Bag Shelter 

The next dangerous caterpillar is highly dangerous to dogs. It’s small, lives in Australia, and is extremely deadly… so toxic is this caterpillar that it’s been known to make a horse miscarry when stung!

Their venomous spines administer an anticoagulant. This can result in internal haemorrhaging and is more than enough to kill a dog.

3. Buck Moth 

This is another dangerous caterpillar that can harm your dog if you live in the south-eastern States of the US. Whilst not fatal, it does deliver an extremely painful sting from the branching spines covering its body.

There have been reports that the sting from a Buck Moth caterpillar can result in anaphylactic shock, with possibly fatal allergic reactions. It’s not a caterpillar you would want your dog to eat. 

4. Cinnabar Moth 

This caterpillar is native to Europe and Central Asia and has subsequently been introduced to Australia, New Zealand and the United States in recent years. It is used by humans to control weeds, and this is where the problem lies.

cinnabar moth
The Cinnabar Moth caterpillar – image copyright CJ Sharp on Wikipedia.

Because this caterpillar eats ragwort, the toxins from the weed absorb into its body. When then eaten or chewed by a dog, the toxic elements can seep out leading to breathing trouble, haemorrhaging, and even kidney failure. 

5. Giant Silkworm Moth 

Unless you take your dog for walks in the Brazilian rain forest you should be ok, as this is where this particular terror lives. If it stings you or your dog, expect blood clotting whilst your body starts to eat itself from the insides out.

Bottom line is this; don’t let your dog or you go anywhere near the Giant Silkworm Moth caterpillar. It will and can kill you with its venom.

6. Hag Moth (aka Monkey Slug)

This one doesn’t even look like a caterpillar which probably makes it even more dangerous to your dog. It’s looks like a hairy spider to me and would definitely fascinate your four-legged friend.

And the worst thing about it? You can find them in the United States nowadays. The best thing; they won’t kill your dog but can deliver a nasty sting of venom.

7. Hickory Tussock 

Next on my list of caterpillars that are harmful to dogs is this prime specimen that lives in Canada and some parts of the northern United States. It’s not deadly as such but can cause a severe allergic reaction.

tussock
The Hickory Tussock caterpillar – image copyright The Cosmonaut on Wikipedia.

If you get pricked by one, expect your skin to swell up in a rash similar to that of a poison ivy reaction. It’s not nice and will be very unpleasant for your dog to touch or eat.

8. Io Moth 

This caterpillar species has never been recorded as killing a dog, but they should be avoided due to the mildly poisonous spines on their back. They live in North America and Canada and are extremely common.

If your dog does get stung by this caterpillar, the worst that could happen will be discomfort and a possible bad allergic reaction.

9. Laurel Cherry Smoky Moth 

As with the last entry, this isn’t a caterpillar that you should consider fatal, but it could still present your dog with some nasty internal and intestinal problems if eaten.

Native to Florida, it’s mildly poisonous due to the short yellow hairs that can sting, leave a rash, and then blisters on the skin.

10. Monarch 

Monarchs are caterpillars that are extremely poisonous to dogs, and this time it’s not about their sting or venom. It’s all about what they eat as their own diet; all they chew on is milkweed.

monarch
The Monarch caterpillar – image copyright M Hedin on Wikipedia.

Milkweed is highly toxic to any animals and can kill a dog. Due to the high concentration of milkweed in this caterpillar, it can prove fatal to your dog if ingested.

11. Pine Processionary

This caterpillar might look harmless, but it’s a dog killer. The hair covering the body can release a toxic protein called thaumetopoein (read more on Chemistry World). Should you dog lick this caterpillar, the toxic nature will cause necrosis in their tongue – in other words your dog’s tongue will rot away.

It can be found in Central Asia, North Africa and southern Europe, where it’s been responsible for destroying pine forests. It’s also been recently reported to be now found in the UK… so one to watch out for! 

Handy Hint: Other insects commonly eaten by dogs include stink bugs. Are they poisonous though? I did the research for you.

12. Puss (aka Southern Flannel Moth)

Native to New Jersey, Arkansas, Florida, and Texas, the Puss caterpillar might look harmless, but don’t let that deceive you; it can leave one of the most painful caterpillar stings known to man.

In fact, people have said the sting is so bad that it makes your bones hurt. If your dog comes into contact with the Puss caterpillar it could had a bad allergic reaction which has been compared to a bee sting. 

13. Saddleback 

Found in the east of the USA, the Saddleback caterpillar is toxic to dogs due to the potent poison in the spines. The poison of this caterpillar is so harmful that it can destroy a dog’s blood cells!

saddleback
The Saddleback caterpillar – image copyright G Lenhard on Wikipedia.

Just one small prick from a spine can lead to internal problems and bleeding, and possible breathing problems. Don’t let your dog eat this caterpillar!

14. Smeared Dagger Moth 

This poisonous caterpillar is also found in the east of the United States and is easily identifiable due to the bright yellow stripes down the side of its body. But that is also what can attract a dog.

It probably won’t be a fatal sting but will certainly burn and itch so one to avoid. 

15. Spiny Oak-Slug Moth 

Native to North America and Canada, the spines on this caterpillar are poisonous enough to cause allergic reactions. That might not sound deadly, but if it causes your dog breathing issues, then it can be!

As you might have guessed from the name, this caterpillar is found on oak trees, and will be either a green, yellow, or reddish colour to blend in.

16. Stinging Rose 

Found in the United States, this caterpillar does really deliver a sting like the name suggests. Each spine has a venom gland which inject a toxic poison under your dog’s skin… usually resulting in allergic reactions.

stinging rose
The Stinging Rose caterpillar – image copyright M McCarty on Wikipedia.

The caterpillar is easy to spot. It’s fat, orange, and with large yellow stripes so you can’t miss. Unfortunately, this is also what might attract your dog so keep them at arm’s length. 

17. Variable Oakleaf

Unlike the other poisonous caterpillars in this list, this one doesn’t have toxic spines. Instead it has a rather novel approach of delivering formic acid that can leave a nasty sting.

It’s only found on oak trees but does have a tendency to blend in due to the colourings. You can see some photos of them on the Arkansas University website.

Handy Hint: On the topic of bugs, did you know that most house centipedes won’t be dangerous to your dog. However, there are some centipedes that are poisonous!

Conclusion

The truth is, most caterpillars are totally harmless to your dog. However, that doesn’t make your life any easier unless you know your caterpillars.

The best thing you can do is keep any eye on your dog and seek professional advice if in any doubt.

Disclaimer: I am not a vet. The content in this guide is based on my own research and having spoken to other dog owners. Always consult with your vet.

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I also found some other things that can be surprisingly toxic to dogs. Have a read to find out what you need to know.

Marc Aaron

I write about the things I've learned about owning a dog, the adventures we have, and any advice and tips I've picked up along the way.

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