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Monarch Life Cycle/Stages Stations
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Egg Stage
The egg stage lasts about 3 days. Use a hand lens to look at the egg and leaf surface.
1. Describe its size, shape, and color AND then sketch the egg.
small as a pin head, football/oval shaped with ridges,
clear/white/greenish in color
2.
How does the color change over time? After a few days the top of the egg
turns a dark brown/black color (it’s the head of the caterpillar) and
symbolizes the caterpillar will emerge soon.
3. Where on the leaf is the egg located? On the underside of the leaf (she lays one egg per plant)
4. What is the first thing the tiny caterpillar eats? Its egg, then the tiny hairs on the underside of the
milkweed leaf. (as it gets bigger it starts to eat the leaf).
5. How many eggs do you think a female monarch usually lays on a milkweed plant? One egg per milkweed
plant (but can lay upto 400 eggs, again, 1 per plant so they have a better chance of survival)
Newly born monarch caterpillars are so small they could drown in a raindrop. But in 2 weeks when they pupate, they
weigh almost 3,000 times as much. If an 8 lbs new-born human baby could grow that fast, you would weigh as much
as a school bus when full grown.
Instars
Younger Caterpillars
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Caterpillar growth is affected by temperature and humidity: they grow faster in warm, moist air than in cool, dry air
(they can overheat in direct sunlight and will stop growing if left near an air conditioner).
Monarch caterpillars molt (shed their skin) five times as they grow. The stage between each molt is called an instar.
When the 5th instar caterpillar molts, it becomes the pupa.
Their appearance changes somewhat from one instar to the next. To identify which instar a caterpillar is in, look at
the size of the tentacles on its head, the length of the body, and the markings on its head and feet. Note that the tiny
first star caterpillar has a black head.
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1. What instar is your caterpillar in?
depends on the day you look at it (probably 2nd or 3rd instar)
2. Describe at least 2 kinds of evidence you see that monarch caterpillars have been feeding. Holes in leaves,
droppings (called frass)
3. How do you think a monarch caterpillar prevent itself from falling off the leaf? Legs have grasping feet
and the spin silk to help them hold on to the leaves
Older Caterpillars
1. What is the color pattern of the caterpillars? Black, yellow, white stripes. Face can be black or yellow
depending on instar. Describe differences between caterpillars in the same house? Depends on what
you were looking at
2. How many antennae does the caterpillars have? 2 sets (so 4 antennae), 1 set on head, 1 set on rear
a. Are they the same length on the front and back? Front antennae are longer than back
3. How many legs does the monarch caterpillar have? 16
a. Look at its feet. The 3 pairs of legs behind the head (true legs) are attached to what will become the
thorax of the adult monarch. How are these true legs different from the five pairs of legs (prolegs)
attached to abdomen segments? True legs are grasping legs, prolegs are thicker and can see
the “white socks”
4. Older monarch caterpillars have “white socks” and black “shoes”. Describe your caterpillar.
5. Monarch caterpillars breathe through 18 round holes (spiracles), one pair on each segment. They are usually
hidden in a black stripe. Find one using a hand lens or magnifying glass.
When monarch caterpillars are full-grown they stop eating and go on a “walkabout”. They have been found up to 70
meters away from the closet milkweed, looking for a sheltered location so they can pupate.
Pupa (chrysalis forming)
www.monarchwatch.org/biology/cycle1.htm
A “J” caterpillar becomes a pupa within 24 hours, typically in the morning. Watch the front tentacles. When they
shrivel and droop, the pupa will emerge within 2 hours. When the head drops and the body looks more like an “I”…
the rear tentacles shrivel…and the prolegs get smaller…the pupa will emerge within 30 minutes.
1. What is your pupa hanging from? Webbing/silk button and the cremaster (the thing that looks like a
stem). Its hanging from the black netting of our cage.
Name:________________________________ Date:______________ Block:_________________
A pupa goes through several stages in the first 12-19 hours after the pupa emerges, its outer skin is soft with many
folds and ridges changing in shape and color to a light jade green. Newly emerged pupa are very fragile and should
NOT be disturbed until the outside hardens (after 19 hours). During the last 1-3 days it becomes a “dark pupa”
revealing the butterfly inside.
2. Which stage is your pupa in? green chrysalis
3. Does your pupa still have its skin attached or was it able to shake it off? No, skin fell off all of ours.
4. Look at the pupa. Try to find the adult wings, antennae and the proboscis. The 2 pairs of gold dots closest to
the ground are associated with the adult’s large compound eyes.
Adult Stage
The adult uses its antennae to hear, taste and smell (it can taste in four places… with their
antennae, proboscis, feet and even with their hind end). The adult female “tastes” milkweed
leaves with her feet before she lays an egg on it. Be careful not to damage feet when
handling butterflies.
1. Look at the graph, when do most monarchs emerge from the chrysalis? Didn’t
include graph, so skip this one.
2. The 3 main body parts of the adult are the head, _thorax________, and __abdomen___________
3. How many wings does the adult have? 4
4. What is a way to tell the males from the females? Males have tiny black dots in the middle of the black
veins on the bottom wings. (black veins are also a bit thinner, but this is very difficult to detect to
our eyes)
5. Find the proboscis (mouth) and see how it looks like a coiled drinking straw.
6. Look at the feet. Describe then and sketch them. Notice the little claws, what are they used for? Little
claws are on the true legs, helps them hang on to the leaves
Common Milkweed
Swamp Milkweed
Common Milkweed
Monarch caterpillars only eat milkweed. There are at least 2,400 different kinds of milkweed in the world. Common
Milkweed (Asclepias syriaca) is found across many states. Break a piece of leaf off the plant to see the milky white
sap.
1. Look at the sample of common milkweed and describe its appearance. thicker stem, with opposite
leaves that alternate as they go up the stem of the plant. Leaves are about 1-2 inches wide and
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about 2-4 inches wide, leaves are hairy underneath, but soft. Can have a pod (filled with seeds),
can have whitish flowers
2. Feel the underside of the leaf and describe what it feels like. Soft and a bit hairy
3. Notice that the leaves grow out from the stem in pairs. How are the pairs arranged as they go up the stem?
Opposite each other and alternate as they move up the stem
4. Compare the leaves of the swamp milkweed to the common milkweed. How are they different? Swamp
milkweed leaves are much thinner in width than common milkweed. Swamp milkweed leaves are
about ¼ - ½ inch wide. Have pink flowers
5. What other interesting characteristics does the milkweed have (flowers, etc.)? only our swamp milkweed
had flowers on it. Some of our milkweed had aphids on it.