The MONARCH BUTTERFLY (Danaus plexippus) is native to North and South America. Monarchs belong to the Family Nymphalidae and Subfamily Danainae which includes milkweed butterflies. Their Genus is Danaus and Species is plexippus. Monarch caterpillars (larvae) are specialist herbivores, meaning they feed on specialized plants. Can you think of other animals that are herbivores? Monarch caterpillars eat only plants in the milkweed family (Asclepiadacea). They gain an important toxin from milkweed that protects them from many predators (caterpillars eating Asclepias curassavica – right). Most birds know that eating monarchs will make them sick so they steer clear. However, there are a few types (species) of birds that can tolerate the toxin in monarch butterflies and their caterpillars. Though monarchs are not safe from all predators. Their larvae and chrysalides (pupae) can be parasitized by parasitoides, most commonly the tachinid fly or parasitic wasp. Monarchs can also be infected with Ophryocystis elektroscirrha or OE which is a protozoan spread by infected adult monarchs through contact. Although we might prefer that all monarch caterpillars become healthy butterflies, parasites are a natural part of maintaining balance in the ecosystem.
AN AMAZING MIGRATION ~ Monarchs have three to four generations of offspring each year. In the fall, the fourth generation flies (migrates) to warmer climates to spend the winter (November to March) as an adult butterfly. Can you think of other animals that migrate? The life span for adults depends on if they migrate. For example, the fourth generation can live up to 9 months but the earlier generations live only two to five weeks. There are primarily three populations of monarch butterflies worldwide. They include the EASTERN MONARCHS (breeding east of the Rocky Mountains), the WESTERN MONARCHS (breeding west of the Rocky Mountains), and a non-migratory population breeding in southern Florida, Hawaii, the Caribbean Islands, and Central and South America. Monarchs have also been introduced in Australia. The eastern monarch population is famous for its long distance migration. Monarchs may travel up to 2500 km from as far north as Canada to wintering sites in the mountains of central Mexico. They spend their winter in the oyamel fir forests on branches that help them stay not too cold and not too warm. The western monarch population migrates shorter distances to winter homes along the central and northern coast of California (a cluster of migrants – left). They may travel from as far south as Arizona or from as far north as Canada or Washington. They primarily utilize eucalyptus trees along the coast. Once spring arrives, the winter butterflies begin to mate and leave their winter homes. These 4th generation winter survivors are the reason we have healthy first generation caterpillars in our gardens in spring and early summer. Without these amazing migrants, we wouldn’t have new generations of monarchs to complete the yearly cycle. That is why it is really important that we encourage everyone to plant milkweed in the garden and in nature areas. Monarchs are declining in numbers and they need our help. Don’t use chemicals in the garden and remember, “If you plant it, they will come!” One of the other ways we can help to protect monarchs is through research and conservation of their migration corridors and winter homes. Tracking the movements of monarchs through tagging (a sticker on the wing – left) helps us to learn about their migration behaviors. If you recover a dead monarch with a sticker and call the phone number, researchers can learn where it started, where it died, how far it traveled, and how long it lived. This data will help us protect all monarchs.
Milkweed is a wildflower that is native to the U.S. Growing up to six feet tall, the plant has long, thin, rigid stems, with a spherical cluster of pinkish-purple flowers. The name milkweed describes the milky sap, which contains natural latex. This latex contains alkaloids (nitrogen-based, drug-like chemicals) and cardenolides (natural steroids), which in some species can be toxic. If you watch caterpillars eat milkweed, you’ll notice they eat in a circular fashion. This is thought to keep the caterpillar from getting stuck in the latex. However, the consumption of the cardenolides and alkaloids makes the monarch itself taste terrible to predators. This helps protect monarchs from becoming prey. That being said, milkweed must be handled with care. First, you should never eat milkweed – it will make you vomit. Second, you should avoid getting the sap on your skin or in your eyes. Milkweed is drought-resistant, and it grows best in well-drained soil. The leaves of the plant are broad and oblong, providing lots of food for monarchs. Often, milkweed will attract aphids. However, you don’t have to worry about them because ladybugs will often show up and eat the aphids. This milkweed information was written by Benjamin Vogt and can be found at The Fix website at https://www.fix.com/blog/gardening-for-butterflies/
Tips for Rearing Monarch Caterpillars at home or in the classroom:
- Collect caterpillars from host/food plants in your garden (milkweed) or purchase kits from Educational Science.
- Use a screened habitat to house a potted milkweed plant or feed clippings to caterpillars in a smaller plastic container. Milkweed wilts quickly and caterpillars won’t eat curled leaves. Late instar caterpillars, nearly ready to pupate may be finished off this way but don’t let them run out of fresh leaves (this is more work than a potted plant and not recommended for school sites.)
- Fun to raise with kids in the classroom or at home.
- Never touch or move a caterpillar not in forward motion. The caterpillar may be preparing to molt or pupate, which if interrupted could cause death.
- Recently emerged adults need 2-3 hours to dry their wings. They don’t do well in captivity but can be kept overnight, or for a few days if you introduce regular feeding to them before releasing.
- A sugar/nectar solution can be prepared with five parts water to two parts sugar. It helps to microwave the solution for dissolving, but make sure it is room temperature before feeding.
- Monarchs generally won’t require food until after 24 hours and then need to be held gently by their closed wings with feet touching the nectar or potted flower. If they are thirsty, their proboscis will unfurl. This must be done for 2 minutes, 2 or more times a day. The warmer the temperature, the more feeding is required.
- The Monarch Life Cycle
- Live Monarch Federation – How to grow Milkweed
- Incredible Journey of the Butterflies
- NABA’s Basics of Butterfly Gardening
- Monarch Watch: Monarch Waystation Program
- Monarch Alert, California Polytechnic State University, San Luis Obispo
- Monarch Health, University of Georgia in Athens, GA Monarch Lab, University of Minnesota
Monarch Overwintering Sites in California