Life Stages (determining instars)

Ever wonder about the various stages that a Monarch butterfly goes through? The entire 'process' takes about four weeks-from egg to butterfly. *Note: Click on individual pictures for an up-cl0se-and-personal view!

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A butterfly begins as an egg. The mama Monarch lays the egg (ova; this is called ovipositing) usually on the underside of a Milkweed (Asclepias) leaf.
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The caterpillar (larva) hatches about four days later and eats its eggshell then begins to eat the leaf it has been laid on. This is the 1st instar or stage of a butterfly's lifecycle. In this stage, the caterpillar is really small (about 1/8"), and sort of looks like an ant. It will eat a teeny circular hole in the leaf.

After munching, it will soon stop to rest and it is time to molt (shed its skin). When a caterpillar stops moving for awhile, it does not mean it is dead! Chances are the caterpillar is between instars and is getting ready to shed its skin. Note: Leave it alone. It is vulnerable at this stage...
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2nd instar caterpillars are a little bit bigger, 1/4" or so in length. You can begin to see their 'Monarch' colouring now. They still don't eat a lot-maybe a leaf or two at the most!
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3rd instars are now looking different. They are bigger (5/8" or so) and the colouring is more vibrant. The two pairs of filaments (or tentacles) are longer. The front pair of legs has moved closer to the head. (Caterpillars have three pairs of legs-they are insects, after all!)
4th instars are where you see something new! Check out the prolegs (the 'fake' legs). You will see a small white dot on them now. The length has definitely grown and the caterpillar is now going on 1" long. At this instar, caterpillars eat a LOT! Expect from this point for caterpillars to eat at least one leaf each an hour...
When the caterpillar is in the 5th instar, it has become nice and plump. The black stripes look really soft and velvet-y. Those white dots on the prolegs REALLY stand out. This instar is a fast mover so watch out! It is soon going to be looking for a place to pupate. When it finds its perfect spot, it will hang upside-down, form a 'J,' and molt for the last time. Don't be surprised when you find a skin or black thing after the chrysalis is formed! Remember, each time a caterpillar molted, it shed its skin, right? Same thing happens when that chrysalis is formed!

Note that when a 5th instar caterpillar eats, it will 'break' the petiole in the leaf so that the leaf falls down. So if you see a leaf that looks broken, check under it! There just may be a big caterpillar munching away.

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The pupa (chrysalis) is when all of the special changes take place when the caterpillar undergoes what is called complete metamorphosis. It takes around two weeks. During this time, things are happening inside. The caterpillar is no longer a caterpillar. During this time, there is an awful lot going on; things that have begun while in the larval stage (the wings were even beginning to form as early as during the 3rd instar!).
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At last, a gorgeous butterfly ecloses (emerges) from the chrysalis. Since Monarchs are large butterflies, it will take several hours for the wings to harden. If you spot any reddish or brownish liquid nearby, don't worry as this is meconium and is simply waste material from the pupa. It is NOT blood! Butterflies do not have 'blood' but have what is called hemo-lymph (in case you are truly interested).

Now, a butterfly is ready to be released and enjoyed!

Note on Photos & Content

All pictures and content on MyMonarchGuide are the copyright of tdogmom/MonarchFriend. Permission is granted for personal and educational use only.

some of the adorable clip art found on this website is used with the express written permission of D.J. Inkers