Chrysalises and Cocoons

25 January, 2009

The chrysalis of a Bright Shield Skipper Butterfly
The chrysalis of a Bright Shield Skipper Butterfly
Image: Ross Field
Source: Museum Victoria

Question: What is the difference between a cocoon and a chrysalis?

Answer: Like all insects, caterpillars must shed their skins as they grow. When they become too big for the skin they’re in, caterpillars develop a new skin under their old skin. The old skin then splits and they crawl out of it. When a caterpillar is large enough to enter the next stage of its development – the pupal stage – it stops eating and finds a safe place to pupate.

The caterpillar then prepares to undergo a very special moult. This time when the old skin splits, the skin that emerges from under the old skin is a chrysalis. Both butterflies and moths develop a chrysalis in their pupal stage, but the chrysalises of moths are usually contained inside a woven structure made of silk – a cocoon.

When it is first secreted, the chrysalis is soft and sticky but it soon hardens to form a protective outer later around the developing pupa. During the next few weeks or months, the animal inside the chrysalis gradually turns into a butterfly or moth. When it is ready, the pupal skin splits and a wet, crumpled butterfly (or moth) crawls out. Moths that build cocoons either cut their way out or secrete a special fluid that softens the structure. Once it has emerged, the butterfly or moth then hangs from its resting place until its wings stretch out and dry and its new body hardens.

Chrysalises and cocoons are highly varied in their appearance, but most blend in with their surroundings. As chrysalises and cocoons cannot move around, effective camouflage is their greatest defence. Chrysalises usually resemble leaves (living or dead), but some are brightly coloured. These species are usually poisonous and the bright colours advertise their poison to deter predators. Some species of caterpillars incorporate sticks, dung and bits of leaves into their silken cocoons to disguise them. Others deter predators by weaving the irritating hairs from their own bodies into their cocoons.

Comments (14)

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dina smith 24 May, 2009 17:53
I remember seeing chrysalis as a child in the 1950's that were about 1 1/2 cms long and coloured silver and gold. What were they please? I lived in Newcastle, NSW at the time. Many thanks. DS
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Discovery Centre 14 June, 2009 14:23

Hi Dina,

Normally we require a specimen, or at least of photo, in order to make an indentification (see Guidelines for using Museum Victoria’s Identification Service), however given that you saw your specimen in the 1950s its unlikely you would have either of these - so, I have referred your question to a museum entomologist just in case your description is particularly common or sounds familiar.

We'll get back to you soon with some more information.

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Discovery Centre 25 June, 2009 16:38

Hi again Dina,

Our entomologist has reported that there are nearly 21,000 species of moths and butterflies in Australia, so it is virtually impossible to identify your pupa based on your description alone.

If you ever see one again please feel free to take a photo of it or collect the specimen for us and we would be more than happy to try and place a name on your gold and silver pupa.

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Allison 21 January, 2010 22:16
Hi, We found a silver pupa on a leaf from a tree in our front yard. We have never seen one this colour before so my 7yr old daughter and I where looking to find out what might come out of it and came across this site. We live in Maitland NSW which is a 30 min drive from Newcastle. Could you give me info on where I could send a photo of it. Perhaps it is the same as what Dina saw when she was a child. Thanks Charli and Allison
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Discovery Centre 23 January, 2010 11:38

Dear Allison,

You can send an image of the chrysalis to discoverycentre@museum.vic.gov.au and we will try and have it identified for you.

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Allison 28 January, 2010 19:11
Hello, Our chrysalis has hatched and a black butterfly with white spots on wings and body appeared. We looked up Aus butterflies and found out it was: Euploea core (Cramer, [1780]) Common Crow or Oleander Butterfly DANAINAE , NYMPHALIDAE. The bush we found it on was an Oleander. Thanks Allison
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mike 3 January, 2011 21:44
hi, I recently found an extremely hard brown coccoon attached to our brick house. I actually thought it was some type of spider sac so I opened it up slightly and there was a grub with bright orange and blue legs and a greeny browny translucent body. We have left it in a plastic container with cotton balls. Will it survive? how can we take care of it so it survives? what do you think it is?
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Discovery Centre 5 January, 2011 16:23
Hi Mike, would you be able to take some images and send them to discoverycentre@museum.vic.gov.au We may not be able to identify it just from the larva stage as if it is a moth or butterfly there are an estimated 20,000 species in Australia but we'll do our best.  
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D.Hardy 27 January, 2011 23:17
I found in Port Sorell, Tasmania an unusual grub carrying it's cocoon shaped like a bell flower, The grub was large and black with a white head and the size was about a witchety grub size. I have picture. Would you be able to tell me where I can find out what type of grub it is as I have already showed a number of people in the bush and it is unknown to them.
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Discovery Centre 28 January, 2011 15:35

Hello D

Our entomologists might be able to identify this, however as a rule larvae are much more difficult to identify than adult forms. We suggest you send you photo and your details to us via the Contact Us link at the bottom of this page.

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Angela 28 February, 2011 14:56
hi, I live in the north west suburbs of Brisbane, I have come across the most gorgeous shiny gold cocoon underneath the leaf of a vine, it's about 1.5cm long any ideas what it is?
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Discovery Centre 4 March, 2011 14:13
Hi Angela! Send a photo and details of your find to our free identification service. We'll pass it on to the entomologists who'll do their best to identify it for you!
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Kylie Portela 20 March, 2014 17:10
Exactly as Angela, above, has written. We have a stunning gd and a bronze chrysilis handing from a vine leaf. What species will emerge? How long will it take?
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Discovery Centre 26 March, 2014 17:41
Hi Kylie, the most likely candidate from your description is Euploea core, often known as the Common Crow Butterfly or Oleander Butterfly. Have a look at this link or other online resources. http://lepidoptera.butterflyhouse.com.au/nymp/core.html If the images online don’t match the chrysalis you have feel free to take some images and email them to discoverycentre@museum.vic.gov.au
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