Monarch caterpillars molt (shed their skin) five times throughout their larval stage. The "skin" that is left behind is actually the caterpillar's exoskeleton. An insect's skeleton is on the outside, as opposed to on the instead like mammals, fish, reptiles, amphibians and birds. Endoskeletons provide support inside the body in the form of bones and cartilage, whereas As caterpillars grow, their exoskeleton gets too tight, so they need to shed it in order to continue to grow. Each molt results in a new "instar" stage. Therefore, when the egg hatches, that tiny 2 mm caterpillar is in its first instar stage.
It will molt three more times and grow exponentially over a couple of weeks. Each stage lasts 3-5 days. The fifth and final molt is when the fifth instar caterpillar becomes a chrysalis.
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Clasping Milkweed
Asclepias amplexicaulis
Photo Citations
Naturedigger would like to thank the following individuals for their contributions to the clasping milkweed (Asclepias amplexicaulis) identification slide:
Flower image provided by: Alan Cressler, Ladybird Johnson Wildflower Center
White flower inset image provided by: Brad Grimm, Grow Milkweed Plants
Deep purple flower inset image provided by: Hazech - iNaturalist observation (cropped) CC BY-NC 4.0
Leaf image provided by: Brad Grimm, Grow Milkweed Plants (cropped)
Pod image provided by: Jason K. Sepka, iNaturalist Observation, (cropped) CC BY-NC 4.0
Asclepias amplexicaulis Profile
Common Name(s):
clasping milkweed
bluntleaf milkweed
blunt-leaved milkweed
sand milkweed
Scientific Name:
Asclepias amplexicaulis
Native Range:
AL, AR, CT, DE, FL, GA, IA, IL, IN, KS
KY, LA, MA, MD, MI, MN, MO, MS, NC
NE, NH, NJ, OH, OK, PA, RI, SC, TN,
TX, VA, VT, WI, WV
USDA Symbol:
ASAM
Habitat:
• prairies
• roadsides
• open woods
• meadows and fields
Growing Conditions:
• sandy soils
• full sun
Plant Height:
• glabrous, waxy, whitish surface
• 1-3 feet (0.25-1 meter)
Stem Description:
• smooth
Leaf Description:
• clasp the stem
• broad
• waxy
• leathery
• no petiole
• lighter on underside than top
Leaf Arrangement:
• opposite
Leaf Margin:
• wavy or smooth
Leaf Surface:
• shiny
Flowering Period:
• May through August
Flower Description:
• very large umbel
• pink, green, white, red and deep purple (highly variable)
• occur in a single umbel at the top of the stem
Pod Description:
• smooth
• erect
• 4-5 inches long (10 - 13 centimeters)
• short contorted stalk
• wide in the middle and tapered at both ends
Other Information:
• color is highly variable
• extremely fragrant
• attracts large numbers of native bees
• is considered rare in some states and protected
Similar Species:
• Common milkweed (Asclepias syriaca). Umbel is similar, however, leaves do not clasp stems and stems are hairy. Pods are not smooth, but very bumpy
• Purple milkweed (Asclepias purpurascens), has a terminal umbel and color is deep rose. Also has broad leaves, but they are petiolate not clasping
Locate and Purchase Seeds (when available):
Xerces Society Milkweed Seed Finder
Milkweed and Wildflower Vendors
For More Information About This Species Visit:
Lady Bird Johnson Wildflower Center
Xerces Regional Milkweed Guide