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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Common Milkweed
Asclepias syriaca
Photo Citation
Naturedigger provided all images of common milkweed for this slide.
Asclepias syriaca Profile
Common Name(s):
common milkweed
Virginia silk
silky swallowwort
Scientific Name:
Asclepias syriaca
Native Range:
United States:
AL, AR, CT, DC, DE, GA, IA, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, VA, VT, WI, WV
Canada:
Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Newfoundland and Labrador *uncommon
USDA Symbol:
ASSY
Habitat:
• old fields
• roadsides
• disturbed or waste areas
Growing Conditions:
• full sun
• sandy or clayey soils
• well-drained loamy soils
• moist soil
Plant Height:
• 3-6 feet (1-2 meters)
Stem Description:
Leaf Description:
• 4-8 inches (10-20 centimeters) long
• 2-4 inches (5-10 centimeters) wide
• shape varies from oblong, ovate to lanceolate
• top of leaf is often darker and richer in color than the bottom
Leaf Arrangement:
• opposite
Leaf Margin:
• entire
Leaf Surface:
• top is smooth and medium to dark green
• underside is woolly and light green
Flowering Period:
June through August
Flower Description:
• drooping umbels with up to 100 flowers (generally less)
• white, purple, light pink or yellow flowers
• petals reflexed backwards
• white, pink or yellow hoods and horns
Pod Description:
• 3-4 inches (7-10 centimeters) long
• covered with hair and soft spikes
• wide in the middle and tapered at the end
Other Information:
• extremely fragrant
To 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