- The only way that butterflies can defend themselves from predators is by making themselves unpalatable to their enemies.
- Many butterflies lay their eggs on plants that are toxic to other insects so that their larvae can ingest these toxins and become poisonous to animals that prey on them.
- These butterflies are toxic to their predators but harmless in every other way. You can support them by growing the plants that they lay eggs on.
Butterflies are fragile and vulnerable to predation by all kinds of critters, from birds to reptiles to spiders to other insects. Sometimes caterpillars of one species will eat the caterpillars of another. Because of this, butterflies have evolved strategies to protect themselves. Some butterflies have eyespots on their wings that startle or confuse predators. Others have camouflage that lets them mimic leaves or bark. Others, ironically, are brilliantly colored, which lets a predator know that they may be poisonous or toxic. This is called aposematism.
Butterflies aren’t venomous because, lacking stingers, spines, fangs, or piercing mouthparts, they have no way to inject their toxins into an enemy. There are venomous caterpillars, however. The puss caterpillar, also called the asp, has spines that can deliver redness and swelling as well as incredible pain. The venomous giant silkworm moth caterpillar of South America and Central America is downright dangerous. Being stung with its spines has been known to cause death.
The toxins that most poisonous butterflies have aren’t potent enough to kill a large predator, but they are potent enough to make the butterfly taste so bad that a predator learns to avoid other members of the species in the future. Interestingly, most butterflies are not poisonous, but many imitate and hang out with other species of butterflies that are. The very distasteful monarch butterfly, for example, is mimicked by the viceroy, which also doesn’t taste good.
Many butterflies start storing the poisons that make them unpalatable in their bodies when they’re caterpillars. The caterpillars feed on poisonous plants, such as milkweed, and those poisons survive the caterpillar’s pupation. There are butterflies who also take nectar or, in rare cases, pollen from poisonous plants. Here’s a list of some butterflies that are toxic:
This butterfly is notorious for the beauty of its orange, white and black wings, its long migration, and its toxicity. The butterfly lays its eggs almost exclusively on milkweed plants, which are poisonous. As the caterpillar eats the leaves of the plant, it collects toxins called cardiac glycosides which persist mostly in the wings and the abdomen of the adult. Some clever predators seem to know this and avoid those parts of the butterfly. A monarch butterfly that feeds from butterfly weed, which is a popular plant people put in their gardens to attract butterflies also collects toxins.
Go here to learn more about the monarch butterfly.
#9. Red Lacewing
This beautiful butterfly of Asia and Southeast Asia also has wings that are colored orange, black, and white like the monarch, though the pattern on the wings is different. Still, the colors should warn predators that this insect is toxic. The caterpillar feeds on the passionflower and is armed with venomous spines.
With a wingspan of a bit over 3 inches, the red lacewing has two female forms. The first one is red, black, and white like the male, and the other is brown with white markings. The underside of this butterfly can be said to be even more beautiful than the top, for it’s covered with a lacy scribble of orange, white, and black lines.
#8. Zebra Longwing
This long-lived, long-winged butterfly gets both its long life and its toxin from the pollen it eats and the poison it stores as a caterpillar as it eats the passionflower. Pollen is converted in its body to toxins called cyanogenic glycosides. This not only protects the butterfly but can protect the caterpillar even before it’s born, as the female butterfly redirects her toxins to her reproductive system when pollen levels are low.
The zebra longwing is unmistakable with its long, oval wings adorned with black and white zebra stripes and red dots. Found in the southern United States and south into South America, it has a 2.8 to 3.9-inch wingspan and is the state butterfly of Florida.
#7. Pipevine Swallowtail
The glorious pipevine swallowtail is one of the most toxic of the poisonous butterflies. This big butterfly of North America and Central America has a wingspan of 3 to 4.5 inches. Its forewings are black, but its scalloped and tailed hindwings are iridescent blue with white spots on the male. The underside of the hind wings has beautiful orange spots on a blue background.
The butterfly gets its toxins because the caterpillar feeds on the toxic pipevine. This plant is full of aristolochic acid which makes both the butterfly and the caterpillar unpalatable to their prospective predators. Because of the pipevine butterfly’s defense mechanism, a good number of butterflies mimic it, including the spicebush swallowtail. Interestingly, there are species of pipevine that are dangerous even to the caterpillars, and the female pipevine butterfly has to be careful where she lays her eggs.
#6. The Postman
Like the zebra longwing, which is a relative, the postman butterfly eats pollen, a rare behavior in butterflies. Another butterfly whose caterpillars eat the poisonous passionflower, the postman shares the zebra’s basic shape, but its wings come in gorgeous patterns of red and black or yellow and black, and there are different morphs depending on where the butterfly is found. Because it’s toxic, many butterflies mimic the postman and fly with it to give them some protection from predators. The postman is not only bad tasting but has a strong smell that even humans can sense.
The postman, which has a wingspan of 2.5 to 3.25 inches, is found in the forests and open areas of Central America and as far south as southern Brazil.
#5. Queen Butterfly
The queen butterfly is another milkweed butterfly, though the levels of alkaloids and cardenolides that its caterpillar stores and passes on to the adult can vary. The queen caterpillar does not have to feed exclusively on the poisonous milkweed but can thrive on plants such as honey vine and dogbane. The queen is a large, beautiful butterfly with a 3.1 to 3.3-inch wingspan and orange-brown wings bordered and veined with black. White spots on its forewings and in its black wing borders seem to glow. Found in both North and South America, it’s found in a variety of habitats, including marshes, forest edges, fields, and even deserts.
#4. Atala Butterfly
This little butterfly is unusual because the male’s abdomen is brilliant red, and its wings are metallic blue with metallic blue dots edging the hindwings. Its coloration and the bright red and yellow colors of its caterpillar warn predators that it’s bad tasting. It is a member of the Eumaeus genus, which is famous because a good number of its members are toxic.
The Atala, with a wingspan of only 1.5 to 1.75 inches, is found in southern Florida and south to the Greater Antilles. It gets its toxins from the cycad, an ancient plant that has been around since before the dinosaurs. It gives the Atala a poison called cycasin, which is notorious for destroying the liver if it’s ingested. Because this butterfly tolerates the cycad as well as it does, scientists believe the insect must be nearly as ancient. The flight of the Atala is leisurely as if it had nothing to worry about from predators.
#3. Common Indian Crow
The common Indian crow resembles the queen and does belong to the same family. But its wings are black and more elongated, and it is a bit bigger with a wingspan of 3.25 to 3.75 inches. It’s also found in Asia and Australia as opposed to North and South America. This butterfly gets its poison from oleander and milkweed. Like other toxic butterflies, it is mimicked by perfectly edible others, including the Malabar raven, the great eggfly, and the common mime.
Besides being inedible overall, the common Indian crow plays dead when it’s attacked by a predator and releases a nasty, toxic liquid that makes the predator let go of it and vomit.
#2. Birdwing Butterflies
These are some of the largest butterflies on earth, and most of them are poisonous. They are also astonishingly beautiful, and their beauty has made them the target of collectors. This, in turn, has caused many to be listed as endangered. Birdwings are native to the rainforests of Asia, Australia, and Southeast Asia. Like the pipevine swallowtail, the caterpillars of birdwings eat pipevine and birthwort and thus accumulate aristolochic acid that persists even when the caterpillars become adults. The caterpillars actually store the poison in the fleshy, spine-like projections that run down their backs. In a species such as the Cairns birdwing, these projections are bright red and warn predators that the caterpillar is poisonous. If a bird or other animal tries to eat the caterpillar or the adult butterfly, they’ll become sick, though the poison probably won’t kill them. They will know not to attack the birdwing from then on.
As with the pipevine swallowtail, an exotic pipevine has been introduced into the Australian rainforest. This pipevine isn’t the species that the birdwing uses as a host plant, but it is so similar that the butterfly is tricked into laying eggs on it anyway. The vine is so toxic the caterpillar can’t handle it and eventually dies.
Read here to learn more about the world’s largest butterflies.
#1. Papilio Antimachus
The giant African swallowtail, with a wingspan of between 7.1 and 9.8 inches, is the largest butterfly in Africa. It’s also one of the most poisonous butterflies on earth. Bearing ornate wings of orange and black that may remind you of a tiger, this butterfly is found in the Central African rainforest and has no natural predators. This is because the caterpillar is believed to eat a plant called Strophanthus gratus, a vine that sports flowers as beautiful as the plant is deadly. It secretes a poison called ouabain, which hunters spread on the tips of arrows. When the arrow pierces an animal even as large as a hippopotamus the animal drops dead of a heart attack. The toxin not only protects the butterfly but gives it its glorious colors.
How Long Do Butterflies Live?
After hatching from their eggs, spending 2-5 weeks as a caterpillar and an additional dozen or so days inside of a chrysalis, butterflies emerge from their metamorphosis with a life expectancy of anywhere from 15 days to 2-3 months depending on the species. One notable exception is the Brimstone Butterfly, which is known to live over a year in optimal conditions. With such short lifespans, it’s clear to see why these species of butterfly have adapted to protect themselves by any means their environment can offer them.
Can Butterflies Harm Humans?
Thankfully, the poison present in butterflies is not strong enough to cause serious harm to humans. This also goes for most species of mammals including cats and dogs. If your pet were to ingest a poisonous butterfly it would immediately be able to recognize the error of its ways by its putrid taste- which would more than likely prevent them from consuming enough to hurt them beyond a seriously upset stomach. So don’t let the fact that these gorgeous insects are equipped with toxic tools to protect themselves prevent you from enjoying their presence in your backyard!
Bonus: Could Planting Milkweed Help the Monarch Butterflies Escape Extinction?
If you are of a certain age you probably remember finding a butterfly chrysalis attached to a shrub, putting it in a jar, and watching it emerge as a bright orange and black butterfly. After it got its bearings and dried its brand new wings – so delicately beautiful they seemed to have been painted by tiny fairies – you set it free to flutter into the summer air.
What was once a right of summer for children is now almost extinct – as the IUCN listed the migratory monarch butterfly as endangered in July 2022. Just 30 years ago, hundreds of millions of monarchs were recorded at overwintering sights annually; today, that number has fallen below 80 million.
Monarchs have been following milkweed – the only plant on which their eggs can be laid – around the world for tens of thousands of years. Around 20,000 years ago, monarchs began following milkweed southward – as receding glaciers and a warmer climate allowed milkweed to colonize new lands.
In the Americas, the monarchs leave their overwintering sites in the Sierra Madre mountains of Michoacan and Mexico to travel to Texas and Oklahoma to lay eggs on milkweed before the end of their lifespan. These eggs hatch and undergo their complete metamorphosis before traveling hundreds of miles across the U. S. and Canada. A fourth generation develops in the northernmost part of the monarchs range – the great-grandchildren of the butterflies that overwintered in Mexico. That group begins life in Maine before retracing the entire journey back to Mexico – stopping to lay eggs on milkweed along the way.
The distribution of native milkweed species has been drastically affected by the use of pesticides and herbicides, habitat loss due to agriculture, logging, and urbanization, and by fires, storms, droughts, and invasive species associated with climate change. You can do your part to revive the plant and the butterfly by planting milkweed in a sunny spot on your property. It can easily form the backdrop of a sunny garden and will attract a variety of pollinators in addition to the monarch butterflies. Perhaps the milkweed bushes you plant will enable your children or grandchildren to experience the wonder of the monarch butterfly’s metamorphosis – sparking dreams of beauty, transformation and heaven.
Summary Of The 10 Poisonous Butterflies
Butterflies are extremely dependent on the plants on which they lay eggs. The growing use of herbicides has nearly wiped out many of these plants. the best thing you can do to help restore butterfly populations is to plant a butterfly garden made of plants native to your area that support butterfly larvae. These plants contain toxins that are harmful to most insects, however, butterflies rely on them as the only food source for their young.
|Rank In Toxicity To Predators||Butterfly||Plants They Need|
|1||Giant African Swallowtail (Pipilo Antimachus)||Eats a plant called Strophanthus gratus|
|2||Birdwing Butterflies||Pipevine and Birthwort|
|3||Common Indian Crow||Oleander and Milkweed|
The photo featured at the top of this post is © iStock.com/AGD Beukhof
Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.