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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California Milkweed
Asclepias californica
Photo Citations
Naturedigger would like to thank the following individuals for their contributions to the California milkweed (Asclepias californica) identification slide:
Flower image provided by: Arboretum Amy - iNaturalist observation
(cropped) CC NC-BY 4.0
Inset flower image provided by: Christian Schwartz - iNaturalist observation (cropped) CC NC-BY 4.0
Leaf image provided by: Lee F. - iNaturalist observation (cropped) CC NC-BY 4.0
Pod image provided by: Ken-ichi Ueda - iNaturalist observation (cropped) CC BY 4.0
Asclepias californica Profile
Common Name(s):
California milkweed
round-hooded milkweed
Scientific Name:
Asclepias californica
Native Range:
CA
USDA Symbol:
ASCA3
Habitat:
• grassy flats
• bushy hillsides below 7,000 feet (2,100 meters)
• open woods of California
• sandy, clay and rocky soils
Growing Conditions:
• full sun
• drought tolerant
Plant Height:
• 1-3 feet (30-60 centimeters)
Stem Description:
• thick, white and woolly
• may be erect, but typically run along the ground or bend
• mature plants have multiple stems
Leaf Description:
• ovate
• oblong to lanceolate
• 2-7 inches (5-18 centimeters) long
• 1-3 inches (2.5-7.5 centimeters)
• very woolly
• sessile or have a very short petiole
Leaf Arrangement:
• opposite
Leaf Margin:
• entire
• smooth or wavy
Leaf Surface:
• dense hairs
Flowering Period:
• April through July
Flower Description:
• reddish, purple or cream-colored corolla (petals)
• reddish or deep purple hoods
• lack visible horns
• hoods and stigma are the only part of the plant not covered in hairs
• underside of petals may be hairy
• buds are very woolly
• reflexed corolla (petals)
• droop rather than stand erect when fully open
Pod Description:
• green turning light brown as it matures
• covered with short hairs
• 3-4 inches (7.5-10 centimeters) long
• 0.75-1.5 inches (2-2.5 centimeters) wide
Other Information:
• endemic to California
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