Poisonous Caterpillars: As the spring comes to the forests and glades, and everything is painted green, we may eagerly await the blooming season. The pleasant aroma of flowers brings bright-colored butterflies to meadows and gardens. However, there is a downside to this: butterflies cannot appear without getting through the caterpillar stage.
Table of Contents
- How do caterpillars become poisonous?
- Top 15 Poisonous Caterpillars
- Buck moth caterpillar
- Saddleback caterpillar
- Monkey slug caterpillar/Hag moth caterpillar
- Hickory tussock caterpillar
- Southern Flannel moth caterpillar or puss caterpillar
- Spiny oak slug moth caterpillar
- Io moth caterpillar
- White flannel moth caterpillar
- Stinging rose caterpillar
- American dagger caterpillar
- Smeared Dagger Moth
- Laurelcherry Smoky moth
- Variable Oakleaf Caterpillar
- Pine processionary caterpillar
- Giant silkworm moth caterpillar
- Does a caterpillar being poisonous really help it?
Those worm-like creatures are, in a way “butterfly kids“. They exist to feed on the leaves, grow, make cocoons and provide enough energy for a future butterfly. Caterpillars are usually not very well liked.
After all, they eat leaves – and thus destroy plants. However, some caterpillars are not just a nuisance. They can be pretty dangerous for those who try to touch them or to eat them.
Gardeners may hate caterpillars because they destroy fruit trees and bushes, but many animals love to eat them. Caterpillars have to be wary of multiple predators. They employ various protective strategies to avoid being eaten!
For example, their coloring can allow them to hide in plain sight through camouflage. Different species form colonies. However, we shall now discuss a third, much more daring survival strategy.
Several caterpillars develop chemical warfare – they become poisonous. Moreover, some have developed poisons that can literally kill a human.
How do caterpillars become poisonous?
There are several methods the insects can use to become poisonous.
- Some caterpillars feed on poisonous plants like milkweed, and storing poison inside; others leak acids.
- However, the most dangerous caterpillars have developed their own detachable weapons containing potential chemical warfare.
- The latter group is quite numerous, and one can find caterpillars with stinging hairs in the Americas, Europe, and Australia.
- Here are some examples below.
Top 15 Poisonous Caterpillars
There are many kinds of poisonous caterpillars. One can find them in almost every place on the planet, except probably the South and North Poles. North and South America are exceptionally lucky (or unlucky) in this regard: one can meet more than 15 species of poisonous caterpillars there, and the ones in South America are considered extremely dangerous.
Buck moth caterpillar
The first poisonous caterpillar in our list is Buck moth caterpillar. These caterpillars can be seen in most states of the Southeastern US.
- The caterpillar has a black body with distinct white spots.
- There is a light form of the species that has a body with a greenish coloring and more prominent spots that look like starfish.
- The head and limbs called prolegs are red.
- There are multiple, thin and branching spines covering the body.
- The caterpillars usually come out around July, and the adult moths fly out in autumn.
- The caterpillars prefer to eat oak leaves but can also dine on willow, hazelnut, cherry, and rose, as well as grasses.
- The breakable spines on the caterpillar’s body carry a poison that can cause different reactions, from simple rash or swelling to severe shock.
- This species is a part of the giant silkworm moths family, which also contains big, beautiful butterflies beloved by collectors.
These unique, slug-like poisonous caterpillars can be found in the Eastern United States.
- Saddleback caterpillar has a small, stocky body and resembles a slug.
- Primary body color is brown, and there is a distinct, bright green marking in the middle of the body, with an oval-shaped reddish mark in the middle that resembles a saddle.
- You can quickly notice two stocky, thick thorns on both head and tale that are covered with spines.
- Saddlebacks hatch from the eggs in spring and late winter (February-March), as they need around 5 months to grow and turn into a butterfly entirely;
- This species is a universal feeder and can eat leaves of multiple types of trees including maple, oak, palms, and chestnuts.
- This caterpillar has a potent poison that destroys blood cells. Even a small prick from the poisonous spine can cause asthma, stomachache, and bleeding.
- When attacked, the saddleback tries to shorten its stocky body as much as possible, putting the blackthorns with spine forward.
- The moth of this caterpillar is wholly unremarkable and is painted in mottled brown.
Monkey slug caterpillar/Hag moth caterpillar
The butterflies of this species usually reside in the Eastern States of USA.
- The so-called “monkey caterpillar” has a short, stocky body with nine pairs of bendable “arms” covered in brown, thin hair.
- This caterpillar usually feeds on the underside of the leaves and relies on suction cups to hold on.
- These slug-like critters usually hatch in the spring.
- Unlike real monkeys, these creatures are not picky about food and can be found on leaves of different trees, from oak and elm to apple and cherry.
- The poison of the hair is mild and causes allergic reactions only in particularly sensitive people.
- While the caterpillar itself is called “monkey slug, the adult moth is named “hag moth,” though it is instead an ordinary looking insect with yellowish wings that has nothing nightmarish about its appearance.
Hickory tussock caterpillar
The next poisonous caterpillar in our list is Hickory tussock caterpillar. These are native to Southern Ontario, Canada.
- The body of this caterpillar is painted in black and white: The primary color of the body is white, with thin hair on the sides. There are connected black markings in the middle of the back.
- The front and the rear of the caterpillar’s body is covered with long, black hair that contains poison.
- A prick from the poisonous hair results in a rash or a swelling similar to poison ivy.
- People that are sensitive to the tussock caterpillar poison may develop severe allergic reactions or feel nauseous.
- The caterpillars are specific feeders and prefer hickory, walnut, elm and oak leaves.
- It is better to be wary of these critters from July to September when they actively roam and feed.
Southern Flannel moth caterpillar or puss caterpillar
The puss caterpillar is widespread in the Southern States, including New Jersey, Arkansas, Florida, and Texas.
- The young caterpillars look relatively ordinary – small, thin, yellow and covered with hairs that stick from the sides.
- The caterpillars at the last stages of growth have a slug-like tiny body covered with many orange or bright yellow hairs that resemble fur.
- The poison of the mature caterpillar is highly dangerous and can destroy blood cells.
- People who touch the animal usually feel the burning pain immediately, which is then followed by a rash that looks like an imprint of the spines.
- Then the people may develop bleeding, difficulty breathing and other dangerous symptoms.
- There were reports when schools were closed in Texas due to the abundance of puss caterpillars. These insects prefer oak and citrus trees that often grow near schools and kindergartens, and children often try to grab them.
Spiny oak slug moth caterpillar
Spiny oat slug moth caterpillars are the next poisonous caterpillars in our list. They live in most eastern states in the US up to the northern areas of Ontario, Canada.
- The caterpillars can appear twice a year in warmer areas and only once a year on spring in colder ones.
- This caterpillar is more conventional. The body can be light green, yellow, reddish or orange.
- This caterpillar feeds on oak leaves exclusively.
- The body of the spiny oak slug moth is covered with thick branching horn-like structures with tiny short spines on them, resembling holly trees.
- The spine’s poison causes mild allergies.
Io moth caterpillar
Io moth butterflies and their caterpillars can be found in Cape Cod and Massachusetts, sometimes in the Gulf States and New England.
- As they grow, the caterpillars change their color from reddish brown with black spines to light green with reddish-white stripes.
- The spines of Io moth caterpillar are arranged in distinct “bouquets“.
- This caterpillar is not a picky eater and feeds on many types of trees – maples, cherries, birches, even cranberry, and gooseberry plants.
- The spines arranged in “bunches” are mildly poisonous. Usually, cause allergic reactions.
- The moth of this species usually active in the afternoon and evening and have distinct “eyes” on the lower wings.
White flannel moth caterpillar
A relative of the southern flannel moth caterpillar, this poisonous caterpillar can be found in Lousiana, Mississippi, Alabama, and Tennessee.
- Unlike its more famous relative, white flannel moth caterpillar has a dark-colored, small body with round, yellow-colored patches.
- There are puffs of stinging black hair on the back.
- The head and tail of the caterpillar are orange, in contrast to the rest of the body.
- White flannel moth caterpillar possess stinging hair that cause pain, sometimes allergy and swelling.
- Another distinct feature of the white flannel moth caterpillar is the presence of a chain made of natural black triangle markings between the bright yellow spots.
- This caterpillar prefers hackberry, black locust, and redbud.
Stinging rose caterpillar
This peculiar poisonous caterpillar lives in many States west to Texas and Oklahoma, including Florida, New York, Philadelphia, and Illinois.
- The appearance of the stinging rose is very striking: the caterpillar has a bright yellow or orange body that has a signature purple stripe running along the back. There are also reddish lines on either side of the caterpillar’s body.
- The poison is contained in the stocky yellow horn-like structures with smaller and thinner spines that cover the body.
- You risk encountering these spines almost everywhere, as this caterpillar can be found on rose bushes, maples, oaks, poplars, dogwood, and hickory.
- The poison mainly causes allergic reactions, which can be severe in sensitive people and quite mild for others.
American dagger caterpillar
This species is truly American – it can be found throughout the whole Eastern North America.
- The body of American dagger moth caterpillar is short, covered with thin, long green hair.
- Thin, long black spines are protruding among the fur-like hair, forming a whole bunch on the rear end.
- The black thick spine-like hair is the source of poison that can cause a painful rash.
- The caterpillar feeds on most common forest trees, such as oak, ash, and elm.
- Some people can find them on the ground – do NOT pick them up without gloves!
Smeared Dagger Moth
Another member of the dagger moth family, this poisonous caterpillar also lives in Eastern North America.
- The body of the caterpillar is black with bright yellow stripes on the sides.
- Smeared dagger moth caterpillar also has stinging hair that cause severe pain, even allergy and swelling.
- The back of the caterpillar is adorned with bunches of thin, white bristles, reddish at the base.
- The Smeared dagger moth caterpillar can feed on anything from grasses to fruit trees.
Laurelcherry Smoky moth
This mildly poisonous caterpillar lives in Florida.
- This species prefers Carolina laurelcherry to anything else.
- The short and stocky body of this caterpillar is transparent yellow on the sides, with intermittent black stripes.
- The danger comes from the small, short, yellowish hair that covers the body.
- The hair literally stings – the victim first feels pain, then a rash develops on the skin, followed by blisters.
- This caterpillar also has a small hood which can hide his head when necessary.
Variable Oakleaf Caterpillar
This poisonous caterpillar is another resident of Eastern North America.
- As the name suggests, the caterpillar is almost exclusive to oaks.
- If you wish to meet the species – wait for July or August.
- It has earned the name “variable” because it can have different markings on its long, lanky body.
- The only universal feature is the distinct reddish stripe on the back.
- Even if there are different variations, the main colors, the caterpillar wears are red and green.
- Instead of poisonous spines, this caterpillar produces formic acid that stings and can cause allergy.
Moreover, now let us introduce you to two unique representatives of butterflies and moths that live outside the US.
Pine processionary caterpillar
The next poisonous caterpillar lives in Southern Europe.
- The caterpillars of this species are social: they form colonies that travel together from tree to tree.
- The body of the caterpillar is colored green with yellow stripes and is covered with thin, whitish spines.
- This caterpillar feeds exclusively on pine needles, and each colony settles on a pine branch and makes a nest of silk threads.
- The spines can cause only a mild allergy in humans, but they are dangerous for pets, especially dogs.
- Tourists coming to France and Spain are advised to keep their dogs from the processions of caterpillars and to avoid standing under pines in summer, especially if there are caterpillar nests.
Giant silkworm moth caterpillar
The last venomous giant silkworm moth caterpillar is a Brazilian citizen and prefers rainforests.
- The color pattern of the giant silkworm caterpillar is not particularly remarkable – it is mostly brown and green, with a striped pattern.
- The whole body of the caterpillar is covered with thin white spines with multiple branches. The endings of the branches are colored black.
- The venom of this caterpillar can prevent the blood from clotting, causing bleeding and destruction of the body from within.
- The medics around the world actively study this venom, because it can help in the treatment of some heart diseases because of its ability to dissolve blood clots.
- These caterpillars are also guardians: the trees where the giant silkworms reside are not damaged by monkeys or other animals. This way, the trees get high-class protection for the price of the few leaves.
Does a caterpillar being poisonous really help it?
There are many poisonous caterpillars, as you can see. However, it does not mean the poison fully protects them.
- The birds that desperately need protein that the caterpillars can provide find their own ways.
- Some eat caterpillars when they are very young and have weak poison.
- Others develop a resistance to a particular poison that the caterpillars use.
- Of course, giant silkworms are the exception – no known animal can stand up to them.
In conclusion – if you see a bright colored, fluffy caterpillar with suspicious horns or spines – avoid them at all costs. If you must remove them – use protection. Many species pretend to be poisonous, but it is still better to be on the safe side.
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-  – “laurelcherry smoky moth – Neoprocris floridana”. Accessed April 22, 2019. Link.
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