monarch CATERPILLAR STAGE

This page shows photos and videos taken of Monarch caterpillars raised inside, and of some found outside in the garden.
(More general information on the Monarch butterfly can be found here.)

NEWLY HATCHED! (a separate page)

FEEDING
MOULTING
SEARCHING FOR A SPOT TO PUPATE
THE ‘J’ PHASE
TOO CLOSE FOR COMFORT
COLOR VARIATIONS AND BELLY

FEEDING – Monarch caterpillars feed exclusively on Milkweed plants. Sometimes they will gnaw at the base of a flower stem (photo on the right) in order to partially detach it and let it hang down. This seems to make it easier for them to eat the flowers. They will also readily eat other parts of the milkweed plant, such as leaves and young seedpods.

Monarch caterpillars eating various parts of Milkweed plants - © Denise Motard
Monarch caterpillars eating various parts of Milkweed plants – © Denise Motard
Monarch caterpillar munching on swamp milkweed seedpod - © Denise Motard
Monarch caterpillar munching on swamp milkweed seedpod – © Denise Motard
Monarch caterpillars munching on swamp milkweed flowers - © Denise Motard
Monarch caterpillars munching on swamp milkweed flowers – © Denise Motard

Monarch caterpillars will readily feed on immature seed pods:

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MOULTING

Since Monarch caterpillars go through five growth stages (called ‘instars’), they then have to moult four times. After moulting, they eat the shedded moult which gives them a source of protein. However they don’t eat the moult head as can be seen below. When freshly moulted, the caterpillar head, legs and prolegs have a yellowish color, a bit translucent.

Monarch cat just molted - Aug. 18, 2018, 9-23 pm - © Denise Motard
Monarch caterpillar just moulted – Aug. 18, 2018, 9-23 pm – © Denise Motard
Monarch cat new instar has funny-looking leg and head colors - Aug. 18, 2018, 9-26 pm - © Denise Motard
Monarch caterpillar new instar has different-looking leg and head colors – Aug. 18, 2018, 9-26 pm – © Denise Motard
Freshly molted Monarch caterpillar - © Denise Motard
Freshly molted Monarch caterpillar – © Denise Motard
Monarch caterpillar just finished eating its molt - © Denise Motard
Monarch caterpillar just finished eating its molt – © Denise Motard
Monarch cat and its molt - Aug. 18, 2018, 9-25 pm - © Denise Motard
Monarch caterpillar and its moult – Aug. 18, 2018, 9-25 pm – © Denise Motard
A different Monarch caterpillar eating its molt - Aug. 18, 2018, 2-30 pm - © Denise Motard
A different Monarch caterpillar eating its molt – Aug. 18, 2018, 2-30 pm – © Denise Motard
Monarch caterpillar, 1.5 hr after molting - © Denise Motard
Monarch caterpillar, 1.5 hr after molting – © Denise Motard
Monarch caterpillar uneaten molt head - © Denise Motard
Monarch caterpillar uneaten molt head – © Denise Motard
Monarch cat newly emerged from molt - Aug. 18, 2018, 9-26 pm - © Denise Motard
Monarch caterpillar newly emerged from its moult – Aug. 18, 2018, 9-26 pm – © Denise Motard
Tiny Monarch Caterpillar molt, with head below - © Denise Motard
Tiny Monarch Caterpillar molt, with head below – © Denise Motard
Monarch caterpillar eating its molt - © Denise Motard
Monarch caterpillar eating its molt – © Denise Motard

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SEARCHING FOR A SPOT TO PUPATE – When Monarch caterpillars are ready to pupate (turn into a chrysalis), they start looking for a suitable spot. Once they find it, they weave a silk pad and hang upside down from it in a ‘J’ position. This stage lasts for around 10-12 hours.

Apparently in the wild a Monarch caterpillar may crawl a distance up to 30 feet (10 meters) in order to find a suitable spot to pupate.
Usually however a caterpillar will take less than an hour to find a suitable spot, but there are individual differences (or preferences). Of the 17 caterpillars I raised, I had two particularly ‘restless’ (or fussy) ones that kept crawling for hours with no end in sight.
Finally out of concern that they were wasting their energy, I placed them in an enclosed space with a screen on top. They immediately started weaving their silk pad at the same time on the screen (see photo below).
The Monarch caterpillar shown below crawling down the swamp milkweed stems was observed the following day on the fern leaves nearby (photos below). It kept wandering for hours on the fern leaves, seemingly unable to find a suitable spot. After moving it into a nearby lilac, it quickly turned into the ‘J’ phase (see photo further below).

WHEN MONARCH CATERPILLARS ARE READY TO PUPATE, they weave a silk pad (see photos on this page) to hang from. As opposed to spiders that secrete their silk thread from the tip of their abdomen, the spinneret (the organ that secretes the silk thread) of caterpillars is located in their mouth.

Their silk pads are now visible - Aug. 22, 2018 - © Denise Motard
Restless Monarch caterpillars FINALLY weaving their silk pads! – © Denise Motard
Monarch caterpillar crawling down milkweed stems to pupate - © Denise Motard
Monarch caterpillar crawling down milkweed stems to pupate – © Denise Motard
Monarch caterpillar searches a spot to pupate - © Denise Motard
Monarch caterpillar searches a spot to pupate – © Denise Motard

EXTENDING THEIR BODIES: When exploring around for a suitable spot to pupate, Monarch caterpillars can extend their bodies without support quite a bit :

The seemingly endless search for a suitable spot to pupate:

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THE ‘J’ PHASE

When the silk pad is ready, the caterpillar attaches itself to it from its last proleg pair, and slowly lets go of its 4 other pairs of prolegs, one by one. It then hangs upside down in a ‘J’ shape, a stage which lasts around 10-12 hours before it turns into a chrysalis.

Monarch caterpillar in 'J' phase with freshly formed chrysalis - © Denise Motard
Monarch caterpillar in ‘J’ phase with freshly formed chrysalis – © Denise Motard
Monarch caterpillars nos. 14 and 15 FINALLY into 'J'phase - Aug. 23, 2018 - © Denise Motard
Restless Monarch caterpillars now into ‘J’ phase – © Denise Motard
Monarch caterpillar in 'J' phase - © Denise Motard
Monarch caterpillar in ‘J’ phase – © Denise Motard

This video (a bit blurry, sorry) captured the moment the caterpillar lets go of its last pair of prolegs to get into the ‘J’ position.

Here’s why it’s crucial for the Monarch caterpillar to attach itself securely to its silk pad, because it can be windy out there:

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TOO CLOSE FOR COMFORT

Monarch caterpillars don’t appreciate being touched by another caterpillar, and will lunge at them. Yet they don’t show that reaction when we handle them.

Here’s another video of an ‘altercation’ between Monarch caterpillars:

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COLOR VARIATIONS and BELLY

Not all Monarch caterpillars are created equal in terms of color, as can be seen below. Some have more prominent black stripes and for others it’s the other way around, more prominent white stripes.

As for their belly, the section in-between the legs and prolegs looks like a type of grey.

Monarch caterpillar with more black stripes - © Denise Motard
Monarch caterpillar with more black stripes – © Denise Motard
Monarch caterpillar with more white and yellow stripes than black - © Denise Motard
Monarch caterpillar with more white and yellow stripes than black – © Denise Motard
Monarch caterpillar belly is lighter-colored - © Denise Motard
Monarch caterpillar belly is lighter-colored – © Denise Motard

This video gives a good view of the Monarch caterpillar belly color:

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