Monarch Butterfly – My Wildlife Wonders No. 4

• Order: Lepidoptera (scale wings)
• Family: Nymphalidae
• Genus: Danaus
• Species: Danaus plexippus
• Wingspan: Considered a fairly large butterfly, with a typical wingspan from 2.75 to 4 inches
• Weight: Less than half a gram
• Lifespan: “Summer generation” adults live 2 to 5 weeks; migratory “fall generations” live longer, up to 8 to 9 months.
• Diet: Nectar from flowers like milkweed, sunflower, coneflower, ironweed, lantana, zinnia, penta and salvia. Ripe or rotting fruits like bananas, mangoes, and oranges are especially prevalent in tropical regions. Caterpillars feed exclusively on milkweed.

• Natural Predators: Invertebrates like ants, spiders, wasps and lacewing larvae prey on monarch eggs, caterpillars and pupae. Fire ants are major larval predators in some places. Mice, lizards and toads may prey on monarchs at various stages of life. Birds like black-backed orioles and black-headed grosbeaks that can tolerate the monarch’s toxic cardenolides, which make it distasteful or toxic to other predators.
• Parasites: Ophryocystis elektroscirrha (OE) protozoan, flies, wasps, bacteria, invasive swallow-wort are toxic to larvae
• Appearance: Bright orange-red wings with black veins and white spots along the edges. Males are slightly larger than females, with thinner wing veins and small scent glands on their hindwings.
• Variations: 3 distinct species, 6 subspecies, and two color morphs of monarch butterflies have been identified.

• Range: Broad range across North America. The eastern population spans from southern Canada to east-central United States, with over-wintering sites in central Mexico. The western population lives west of the Rocky Mountains, from southwestern Canada to overwintering sites in coastal California. Non-migratory populations also exist in parts of the southern U.S.

• Origin: Native to North America, from central and southern Canada to northern Mexico
• Habitat: Monarchs prefer open areas rich in flowering plants and milkweed, their larval host plant. They can typically be found in meadows, prairies, grasslands, open woodlands and agricultural edges.
• Overwintering forests: They rely on oyamel fir forests in central Mexico and eucalyptus or pine groves on the California coast for microclimates that have shelter, sunlight and moisture that enable over-wintering. They roost at night in trees, clustering by the tens of thousands to keep warm, and bask in the morning sun.

• Mating System: Promiscuous; males patrol milkweed patches to chase off rivals and seek females. Males often mate with multiple females, and females often mate more than once.
• Mating Season: Primarily spring and summer for migratory populations. Over-wintering populations mate in early spring before dispersing.
• Courtship & Copulation: Monarchs mate soon after emerging as adults in spring and summer. Males pursue females in aerial chases, often forcing them to the ground where copulation occurs, lasting 30 to 60 minutes. Males use claspers to attach to females during mating, lasting 30 minutes to several hours. The male transfers a spermatophore that fertilizes the female’s eggs and provides nutrients.

Reproduction & Lifecycles

• Egg laying: Females lay eggs on the underside of milkweed leaves, their exclusive host plant. A female lays between 100 and 300 eggs during her lifetime, usually over days to weeks. Females select host plants guided by chemicals detected through taste receptors on their feet. Monarchs don’t care for eggs or offspring; instead, eggs, larvae and pupae develop on the milkweed plants.
• Reproductive diapause: The last-generation monarchs of the year delay reproduction and do not lay eggs immediately after emerging. This is called “diapause,” during which development is suspended and some physiological processes are dormant. This helps them complete their long migratory flight and survive overwintering.
• Metamorphosis: Monarch butterflies undergo complete metamorphosis, which can take a few weeks up to seven weeks to complete depending on environmental conditions. Less than 10% survive. The monarch butterfly lifecycle includes four phases – egg, larva, pupa and adult.

Migration

The monarch is the only known butterfly to exhibit a two-way migration pattern, similar to many bird species.

• Migratory populations: Monarch butterflies in the eastern North American population instinctively migrate in the late summer and fall from the north and central U.S. and Canada, southward to Florida and Mexico. One generation covers thousands of miles in a migration, then returns north in the spring with multiple generations – as many as three or four at once. The population west of the Rocky Mountains typically migrates to southern California or a bit further into Mexico. They can fly 50 to 100 miles in a day during the migration, totaling nearly 3,000 miles by the end of their journey.
• Non-migratory populations: Additional monarch populations that do not migrate can be found in the southern Americas, Europe, Oceania and Southeast Asia. Migratory and non-migratory monarchs are genetically the same; a part of the non-migratory monarch’s genome that regulates migration is not expressed.