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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Bract Milkweed
Asclepias brachystephana
Photo Citations
Naturedigger would like to thank the following individual for his contributions to the bract milkweed (Asclepias brachystephana) identification slide:
Flower, leaf/stem and pod images provided by: Patrick Alexander,
SEINet portal Network: SEINet (cropped)
Asclepias brachystephana Profile
Common Name(s):
bract milkweed
desert-rose milkweed
short-crowned milkweed
Scientific Name:
Asclepias brachystephana
Native Range:
AZ, NM, TX
USDA Symbol:
ASBR
Habitat:
• mesquite scrub
• desert mountains
• dry plains
• grasslands
• mesas
• disturbed areas of dry alluvial soil
• elevation 3,500-7,000 feet (1,070-2,130 meters)
Growing Conditions:
• Full sun
Plant Height:
• 12-24 inches (30-58 centimeters) tall
Stem Description:
• ascend at an angle or are erect
• clustered
• whitish color due to dense hairs
• hairs may be absent from older stems which will appear greenish
Leaf Description:
• 3-6 inches (cm) long
• linear-lanceolate
• apex is acuminate
• abruptly narrowed at the base into a short petiole
• petiole 0.8-0.3 inches (2-8 millimeters) long
Leaf Arrangement:
• opposite and dense
Leaf Margin:
• 2-5 inches (5-12 centimeters) long
• 0.20-0.8 inches wide (5-20 millimeters) wide
Leaf Surface:
• white and woolly above, smooth below
Flowering Period:
• April through September
Flower Description:
• reddish purple to violet
• petals are oblong-ovate
• corollas reflexed backwards
• 3-8 umbels
• hoods broader than long, toothed on the inner margins
• hoods and horns are yellowish
• horns attached near the middle of the hoods
• petals are approximately 0.2 inches (5 millimeters) long
• flower stalks are 0.4-0.8 inches (10-20 millimeters) long
• 6-12 flower stalks per cluster
• flowers often near the top nodes of the stem
Pod Description:
• 2-4 inches (cm) long
• erect on deflexed pedicels
• oblong
• smooth
• reddish
• white or green striped
Other Information:
• Special value to native bees
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
Western Monarch Milkweed Mapper