Caterpillars going through metamorphosis and emerging from their chrysalises as beautiful, colorful butterflies is one of nature’s most magical wonders. The process of how a creeping, leaf-eating caterpillar transforms into a stunning, graceful butterfly is fascinating and intricate. In this article, we will explore the anatomical changes, timing, stages, and science behind a caterpillar’s metamorphosis into a butterfly.
An Overview of Metamorphosis
Metamorphosis is the process by which caterpillars transform into butterflies and moths. There are four stages of complete metamorphosis:
- Egg
- Larva (caterpillar)
- Pupa (chrysalis)
- Adult butterfly
It all starts when a female butterfly lays her eggs, usually on leaves of plants that will serve as food for the caterpillars when they hatch. The eggs hatch into larvae, known as caterpillars. Caterpillars spend their time voraciously eating and growing, periodically shedding their exoskeletons through a process called molting as they get bigger and bigger.
When a caterpillar is fully grown, it attaches itself to a stem or leaf and forms a chrysalis around itself. Inside the chrysalis the caterpillar essentially digests itself, breaking down its tissues into a nutrient-rich soup. This soup fuels the rapid growth of specialized groups of cells called imaginal discs into the wings legs, antennae, and other adult body parts of the future butterfly. When metamorphosis is complete, the mature butterfly emerges from the chrysalis ready to find food, mate, and start the life cycle over again.
Caterpillar Anatomy
Caterpillars are well suited for their primary activity – eating, They have strong mandibles for chewing leaves and sharp reaction time to potential predators Their bodies are soft and flexible with many segments to allow them to inch along branches and reach tender new leaves,
Some key anatomical features of caterpillars include
- Head – Contains the mouth, eyes, and antennae
- Thorax – Consists of three segments, each with a pair of jointed legs
- Abdomen – Made up of 10 segments, contains digestive system and silk glands
- Prolegs – Unjointed leg-like structures on abdominal segments 3-6 and 10 that help clasp onto surfaces
- Spiracles – Paired openings along the sides that allow air exchange
- Crochets – Curved hooks on the prolegs that grip surfaces they walk on
As caterpillars grow through successive molts, these anatomical features become more defined. Once the caterpillar is fully mature, the process of metamorphosis into a butterfly begins.
Life Stages of Metamorphosis
Metamorphosis from caterpillar to butterfly consists of four main life stages:
1. Egg
- Female lays eggs, usually on leaves of caterpillar’s host plant
- Eggs hatch within 4-10 days, releasing larvae
2. Larva/Caterpillar
- Larva eats leaves voraciously, grows through molting
- Sheds exoskeleton 4-5 times as it outgrows each skin
- Full grown larva stops eating and searches for place to pupate
3. Pupa/Chrysalis
- Larva sheds final skin and forms pupa around itself
- Inside pupa, tissues are broken down into nutrient soup
- Imaginal discs use soup to rapidly grow into adult structures
- Metamorphosis into butterfly complete in 1-2 weeks
4. Adult Butterfly
- Butterfly emerges from pupal case, inflated its wings
- Wings dry and harden before first flight
- Butterfly lives 2-6 weeks, focused on mating and laying eggs
The length of these stages varies by species. The Monarch butterfly’s metamorphosis from egg to adult takes about a month. Swallowtail butterflies need several months. But no matter the timing, this 4-stage life cycle remains the same across all butterflies.
Inside the Chrysalis
The most radical changes happen in the pupal stage inside the chrysalis. As soon as the caterpillar molts its final larval skin, the work of metamorphosis begins.
The caterpillar releases enzymes that digest all of its tissues except for groups of cells called imaginal discs. Before hatching from its egg, the caterpillar developed an imaginal disc for each structure that will appear in the adult butterfly – discs that will become its eyes, wings, legs, antennae, and more. These imaginal discs survive the digestive juices and use the soup of recycled caterpillar tissues to fuel their growth into the various parts of the butterfly.
For example, a fruit fly’s wing imaginal disc may begin with only 50 cells, but increase to over 50,000 cells by the end of metamorphosis. Depending on the species, some caterpillar muscles and nerves are preserved and carried over to the adult butterfly’s body. There is even evidence that some moths can remember lessons learned in their caterpillar stage!
Emerging from the Chrysalis
Two weeks or longer after the chrysalis began forming, the day finally arrives – the mature butterfly is ready to emerge. The chrysalis skin splits open, pushed apart by the butterfly’s legs and swollen body.
At first its wings are small, soft, and folded together. The butterfly hangs onto its empty pupal case, pumping fluids from its swollen abdomen into its wing veins to inflate them. Within an hour the wings are fully open, dried, and ready for flight!
Now a beautiful, winged creature instead of a creeping caterpillar, the adult is equipped for its new focus – finding nectar, choosing a mate, and laying eggs to start the wondrous cycle again.
Fascinating Metamorphosis Facts
- Monarch caterpillars shed their skin 5 times, growing over 2,700 times their original size!
- A Monarch chrysalis completely dissolves into liquid within 24 hours of forming.
- The adult butterfly’s legs, eyes, and antennae were present in the caterpillar as imaginal discs.
- Some caterpillars walk around with tiny wings already forming inside their bodies!
- A caterpillar’s identity is lost in metamorphosis; the adult cells are entirely new.
- The chrysalis stage for most species lasts between 10 to 14 days.
- Some chrysalises hibernate through winter, delaying the adult butterfly’s emergence.
- Swallowtail caterpillars change from brown to green as they mature.
Watching Caterpillars Turn into Butterflies
Being able to observe caterpillars go through the stages of metamorphosis and emerge transformed as butterflies is an unforgettable experience. Many butterfly kits and pavilions allow you to do this.
These kits make it easy to raise caterpillars, providing all the supplies you need and expert instructions. Different kits feature diverse caterpillar species, like Monarchs, Painted Ladies, and Swallowtails. Getting to witness metamorphosis first-hand helps illuminate how caterpillars body-build themselves into winged beauties!
The Wonders of Metamorphosis
The magical process of caterpillars morphing into butterflies and moths astounds scientists and nature lovers alike. As caterpillars eat voraciously, they ready their imaginal discs for the rapid cell division needed to construct the adult insect’s body parts inside the pupa. The ability of butterflies to transform so radically from a crawling caterpillar to a vividly colored, delicate-winged creature is one of nature’s most incredible feats.
How to identify caterpillars
A caterpillar is the larval stage of a moth or butterfly. It is the second part of their four-stage life cycle: egg, larva, pupa and adult. Many caterpillars look very different as they grow, so weve described the larger stages of the caterpillars growth when theyre often more obvious. Some are easily spotted on their favourite food plants. Here are some of the species youre likely to see!
When & where: August-June. A variety of habitats including gardens, but especially damp grassland, marshes and boggy areas.
Description: Up to 7 cm long. Dark and covered with brown hairs and golden speckles. A row of white hairs runs down each side of the body.
Drinker moth caterpillar ©Chris Lawrence
Drinker moth caterpillar ©Tom Marshall
Drinker caterpillar © Guy Edwardes/2020VISION
Young drinker caterpillar © Vaughn Matthews
When & where: June-April, most obvious in spring. Often heathland and coastal grassland.
Description: Up to 7 cm long. Hairy, with long dark hairs on the sides of the body and shorter orange hairs on top. Young caterpillars are dark with orange bands.
Fox moth caterpillar ©David Longshaw
Fox moth caterpillar by Tom Hibbert
Fox moth caterpillar by David Longshaw
Early instar fox moth caterpillar © Frank Porch
When & where: August-June. A variety of habitats including grassland, heathland, fens, and hedgerows. Often found crawling across paths in spring.
Description: Young caterpillars in late summer and autumn are small and bluish with orange diamond patterns. More obvious in spring, when caterpillars are large and extremely furry, with long, orange-brown hairs. There are black bands between each body segment, and white dashes on each side.
Oak eggar caterpillar © Tom Hibbert
Oak eggar caterpillar © Frank Porch
Oak eggar caterpillar © Vaughn Matthews
Early instar oak eggar caterpillar © Frank Porch
Early instar oak eggar caterpillar © Frank Porch
When & where: August-June. A wide range of habitats including gardens.
Description: Up to 6 cm long. An extremely hairy caterpillar, known as the “woolly bear”. Mostly black and ginger, with longer white hairs.
Garden tiger caterpillar © Frank Porch
Garden tiger caterpillar ©Amy Lewis
Garden tiger caterpillar © Faye Davies
Garden tiger caterpillar © Brian Eversham
When & where: July-September. Found on ragwort in most grassy habitats.
Description: The caterpillars of this moth are distinctive, with black and yellow stripes – warning predators that they taste terrible. Theyre easily spotted feeding on ragwort.
Cinnabar moth caterpillar ©Andrew Hankinson
Cinnabar caterpillars © Jon Hawkins – Surrey Hills Photography
Cinnabar caterpillar © Niall Benvie/2020VISION
When & where: June-September. A variety of habitats, including gardens. Often where rosebay willowherb is found.
Description: Up to 8.5 cm long. A chunky green or brown caterpillar, with several eyespots at the front end and a spiky tail at the rear.
Elephant hawk-moth caterpillar ©Dawn Monrose
Elephant hawk-moth caterpillar © Tom Hibbert
Elephant hawk-moth caterpillar © Vaughn Matthews
Elephant hawk-moth caterpillar © Tom Hibbert
When & where: July to September. Widespread in southern England and Wales. Found in a variety of habitats, including gardens.
Description: Up to 8.5cm long. Green and chunky, with purple and white stripes on the body and a black and yellow horn on the rear.
Privet hawk-moth caterpillar ©Roy Bedborough
When & where: June to September. Widespread in a variety of habitats, including parks, gardens and wetlands. They feed on poplars and willows.
Description: Recently hatched caterpillars are tiny and black, with two long, whip-like tails. Older caterpillars are plump and green, with a dark, white-edged saddle. The head is surrounded by a pink patch, with false eyes making it look like a giant face. They still have two thin tails. When theyre fully fed and ready to pupate, they turn a purplish colour.
Puss moth caterpillar ©Vaughn Matthews
Puss moth caterpillar © Vaughn Matthews
Puss moth caterpillar © Tom Hibbert
Newly hatched puss moth caterpillars © Frank Porch
When & where: April-July. A range of open habitats, including gardens. Feeds on mulleins and buddleia.
Description: Distinctive whitish caterpillars, with yellow splodges across the body and large black spots.
Mullein caterpillar © Frank Porch
Mullein moth caterpillar ©Chris Lawrence
Mullein caterpillar © Frank Porch
Mullein caterpillar © Frank Porch
When & where: August-June. Scrubby habitats including hedgerows, woodland and gardens.
Description: Black with long, greyish-white hairs. On top it has a pair of red lines, with a row of white blotches either side of them. A red line runs along each side. The hairs can be an irritant.
Yellow-tail moth caterpillar ©Chris Lawrence
Yellow-tail caterpillar © Tom Hibbert
Yellow-tail caterpillar © Tom Hibbert
When & where: August-May. Scrubby habitats, including coastal scrub.
Description: Black with long brown hairs, two red spots on top and a line of white marks along each side. Found in conspicuous communal webs on food plants. The hairs cause skin irritation.
Brown-tail moth caterpillar © Tom Hibbert
Young brown-tail caterpillar © Chris Lawrence
Brown-tail caterpillar © Frank Porch
When & where: June-October. Grasslands, wetlands, heathlands, open woodlands, and coastal habitats.
Description: Black with brown hairs. Row of alternating red spots and lines on top, with a line of white dashes either side. Row of spots and dashes on each side. Rests with slight hunch in the back.
Knot grass caterpillar © Vaughn Matthews
Knot grass caterpillar © Frank Porch
Knot grass caterpillar © Frank Porch
When & where: May-July. Common in a range of habitats where common nettle is present.
Description: Up to 4.5 cm. Black with black spines and small white dots. Found in communal webs on common nettles.
Peacock caterpillar © Margaret Holland
Peacock caterpillars ©Vaughn Matthews
Peacock caterpillars © Jon Hawkins – Surrey Hills Photography
When & where: May-September. Commonly found in a variety of habitats including woodland, parks and gardens.
Description: A funky-looking grey and black caterpillar, with large tufts of hair, including a mohawk of yellow tufts on the back. Large caterpillars can often be spotted in late summer on a range of shrubs and trees.
Vapourer caterpillar © Pete Richman
Vapourer caterpillar © Les Binns
Vapourer moth caterpillar ©Tom Hibbert
When & where: June-October. Found on a wide variety of deciduous trees and other plants, including bramble.
Description: A striking bright green caterpillar, with black bands between its body segments, yellow/whitish hairs, a row of yellow tufts on top and a red tuft at the rear.
Pale tussock caterpillar ©Lizzie Wilberforce
Pale tussock caterpillar © Frank Porch
Pale tussock caterpillar © Frank Porch
Sawflies are a group of flies, whose larvae look very similar to moth and butterfly caterpillars. The larvae are usually 1-4 cm long, but come in an impressive variety of colours. One way to spot a sawfly larva is to count the legs – they also have six true legs, but usually have six or more pairs of the stumpy prologs, whereas caterpillars have five or fewer.
Rose sawfly larvae ©Les Binns
Iris sawfly © Tom Hibbert
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Monarch Butterfly Metamorphosis time-lapse FYV
FAQ
What kind of caterpillar turns into a butterfly?
Watch a monarch caterpillar transform into a chrysalis, emerge as an adult and take its first flight! Monarch caterpillars feed on milkweed and develop through five instars, or growth stages, before forming a ‘J’ shape and transforming into a chrysalis.
How long does it take a caterpillar to turn into a butterfly?
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The caterpillar, or larva, grows and molts (sheds its skin) multiple times as it eats and stores energy.
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Once fully grown, the caterpillar forms a chrysalis, also known as a pupa, where it undergoes its transformation.
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After a period of time in the chrysalis, the adult butterfly emerges.
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Timing:
- Smaller butterfly species: The entire process can take about 2 to 4 weeks.
- Larger species, like Monarchs: The process can take up to 6 weeks or longer.
- Monarchs: The caterpillar stage lasts about 2 weeks, and the chrysalis stage lasts 8 to 15 days.
- Smaller butterfly species: The entire process can take about 2 to 4 weeks.
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Factors affecting the duration:
- Species: Different butterfly species have different life cycles.
- Environmental conditions: Temperature, humidity, and food availability can influence the length of each stage.
- Time of year: The length of the cycle can vary depending on the time of year.
- Species: Different butterfly species have different life cycles.
Do black fuzzy caterpillars turn into butterflies?
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These are fuzzy, black caterpillars that are common across the U.S.
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The adult stage of these caterpillars is the Isabella tiger moth, a moth with a light yellow or orange color and black spots.
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It’s important to note that moths and butterflies belong to the same order of insects (Lepidoptera), but they are distinct.
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Another type of fuzzy black caterpillar, the salt marsh caterpillar, turns into a white moth with black spots.
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Solid black woolly caterpillars are the caterpillar stage of the giant leopard moth.
Are milkweed tussock moth caterpillars poisonous?
One reason for all the attention they receive (during late summer and early fall) is that, unfortunately, the hairs on these caterpillars can cause a very itchy rash. The prickly hairs are a defense mechanism (the hairs are not poisonous or venomous).