What Do the Colours of Caterpillars Mean?

There are about 20,000 species of butterflies and 150,000 species of moths in the world, both of which come from caterpillars. This is why the variety of shapes, sizes and colours you see in caterpillars is so great. But, what do the colours of caterpillars mean?

Generally, brightly coloured caterpillars are poisonous, and predators should avoid going near them. Caterpillars that have the same colour as leaves and trees are for camouflage. 

Caterpillars come in all pretty colours and shapes. Bright colors usually indicate that the caterpillar is very poisonous, and predators should maintain distance from them.

Caterpillars may also change colour as they grow larger from an earlier stage to a newer one. Or for camouflage related purposes, caterpillars also change colors as most species don’t have enough defensive mechanisms to protect themselves against predators.

They simply hide by changing colours on the surface they’re on, for example, a tree, twig, a leaf or plant.

Do Caterpillars Have the Same Colours as the Butterflies?

No, caterpillars don’t have the same colours as the butterfly or moth that they are going to become. In fact, it’s often hard to determine what a butterfly will look like by looking solely at the caterpillar it currently is. 

Where Do Colours in Caterpillars Come From?

Caterpillars often have natural pigmentation meaning their colour will always stay the same wherever and whenever you see them.

However, structural colors meaning the angle from which the caterpillar’s body is being hit by light, will make it seem that its color is changed. It’s a shimmering effect called iridescence

Caterpillars are colourful insects, but most often, their colourful traits name them easy prey for many predators as they can spot them from afar because of their vibrant colouring.

Therefore, most caterpillars adopt colours similar to the places they’re mostly on, such as leaves, trees, plants, and twigs that helps them blend into their natural habitat where they live and feed.

These colors that give caterpillars excellent camouflage are green, yellow, brown, orange, black, and other dull colours. 

Bright coloured caterpillars such as bright black, yellow, or red typically indicate that these caterpillars are poisonous to eat so predators should think twice before eating them. Bright coloured caterpillars also indicate that it’s dangerous to even handle the caterpillar. 

Are Yellow and Black Caterpillars Poisonous?

Several species of caterpillars are yellow and black in colour and they’re commonly found in most trees in the US. Most of the yellow and black caterpillars aren’t dangerous. However some species are poisonous and have irritating quills that can cause a painful sting.

The elegant sheep moth caterpillar and Nevada buck moth caterpillar are two caterpillars that have stinging quills and have yellow and black colored markings.

Buck moth caterpillars are purplish-black with red spines and yellow spots. They’re 2 inches in length. Western sheep moth or elegant sheep moth caterpillars are also black with yellow spines, as the caterpillar ages, they turn orange.

All these caterpillars mentioned are poisonous stinging caterpillars.

Yellow and black caterpillars that are harmless and pose no harm are black swallowtail caterpillars, yellow-necked caterpillars and red-humped caterpillars. These caterpillars are harmless because they don’t have poisonous spikes or quills.

Black swallowtails have smooth green bodies with yellow dots and black bands. Red-humped caterpillars have yellow bodies with black, reddish or white stripes, with red heads and yellow-necked caterpillars are black with white hair and yellow stripes, yellow-necked caterpillars are hairy, but they’re not poisonous. 

Are Green Caterpillars Poisonous?

Green caterpillars are some of the most common types of caterpillars. Some of the biggest and chubbiest caterpillars are green ones. Green caterpillar species vary in shape, size, markings and the food they mostly eat.

Most green caterpillars are completely harmless, and they often have smooth, soft squishy bodies with no quills or spines coming out. 

Though certain species of green caterpillars may also not be poisonous, they have defensive quills and spines to protect themselves from predators. These spines aren’t toxic, but they can hurt a lot if you or any predator comes in direct contact with them.

The European Puss caterpillar is a weird and odd-looking green caterpillar that has two spiked tails and menacing patterns around its head to make it look intimidating and scary. 

This green caterpillar doesn’t sting, but it’s poisonous. It’s one of the more dangerous green caterpillars as it throws its poisonous acid at you instead of stinging it if you or a predator are too close.

To identify if it’s threatened, its tails will whip from side to side, and the caterpillar will raise its head, showing its menacing patterns. 

Are Blue Caterpillars Poisonous?

Caterpillars are rarely in uniform blue when it comes to their many diverse colour ranges. They don’t even shine bluish on the leaves. However, bluish-green caterpillars do exist.

A bluish-green tone often helps caterpillars camouflage. Cecropia Caterpillars are unique and slightly odd-looking fat caterpillars, they’re often quite large in size as well. 

The caterpillars, when they’re newly hatched, are yellowish-green, but as they grow bigger, they start to change into bluish-green.

Rough Prominent Caterpillars, also known as Tawny Prominent or White-Dotted Prominent caterpillars, are slightly bluish in colour tone. 

Eastern Tent Caterpillars, Forest Tent Caterpillars, and Plain Looper caterpillars are all slightly bluish in tone and all of these bluish toned caterpillars that are more green than blue are all harmless and aren’t poisonous. 


Caterpillars come in all peculiar shapes, sizes and colours. Butterflies and moths each have their own odd-looking caterpillars. Caterpillars are colourful insects, and like most other insects in the wild, brightly coloured insects are most often poisonous, and their bright colours are a way of telling predators to back off.

Some bright coloured caterpillars have spines and quills so predators can identify that those caterpillars are poisonous. When trying to get rid of caterpillars, it’s vital that you do so with caution in case the caterpillar you’re dealing with is poisonous.

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