(MCT) – Monarchs should be in your yard by now -- the overwintering population of butterflies left Mexico in late March. Along the migration route, the adults feed on nectar and look for milkweed leaves to lay eggs for succeeding generations.
“Upon arrival, Mama Monarch looks for milkweed,” says Helen Hamilton, retired biology teacher and author of “Wildflowers and Grasses of Virginia’s Coastal Plain.”
“As the caterpillars grow, they feed voraciously on milkweed leaves, often stripping the stems bare. Monarch caterpillars are not affected by the toxic substances in milkweed plants, and those chemicals protect also the adult butterflies from predators. Birds that taste a monarch find them extremely distasteful and will avoid that orange and black coloration.”
Monarchs are seen across the United States, according to the National Wildlife Federation, www.nwf.org . Most thrive east of the Rockies, making their way through Texas and southern corridors as they migrate northward, sometime reaching southern parts of Canada.
Western Monarchs breed in states west of the Rocky Mountains and spend winter in southern California.
Female monarch butterflies lay their eggs exclusively on the leaves and stems of plants in the milkweed family _ Asclepias, which contains about 140 members. These herbaceous perennials usually have milky sap, opposite leaves, and rounded flower heads, densely packed with small blooms that also attract bees, according to Hamilton.
Eight species of milkweed occur along the East Coast and elsewhere _ five are very common. Butterfly Milkweed (Asclepias tuberosa), with light orange to brick red small flowers, prefers dry sandy soil in full sun, and is drought tolerant. The pink-flowered Swamp Milkweed (A. incarnata) grows in moist ground in open areas. Also with deep-pink flowers, Clasping Milkweed (A. amplexicaulis) is found in dry woodlands. Common Milkweed (A. syriaca) has pink flowers and grows in fields, meadows, open woods, and along roadsides. White Milkweed (A. variegata) occurs in upland woods and thickets.
West of the Rockies, you find different milkweeds, including Pallid, which is native to the western region. Learn more about ordering and growing milkweeds through the nonprofit Monarch Watch educational site at http://monarchwatch.org/milkweed... .
Monarch butterflies fly longer and further than any other insect _ more than 2,500 miles to overwintering sites in Mexico, according to Hamilton.
In February and March, overwintering monarchs mate, lay eggs and emerge as adults for the flight north. One generation cannot make this flight: The adults that emerge from pupae in Mexico in late March stop in Texas and other southern states to mate, lay eggs, and complete their life cycle. This second generation flies through southern states to the East Coast, arriving in May or June to mate, lay eggs and feed on milkweed as caterpillars. This third generation lives as adults for about a month during June through August. Late August, they mate and a fourth generation readies mid-September for the long migration to the overwintering grounds in Mexico. These butterflies have a different physiology, turning nectar into fat that fuels their flight to Mexico. They fly along the eastern mountain valleys, utilizing thermals as much as possible to conserve flight energy, according to Hamilton.
Other populations leave Mexico for summer homes in the corn belt. This population is greatly stressed from loss of habitat as corn fields have expanded, according to Hamilton. The clean energy act of 2007 provided a mandate for farmers to grow more corn as biofuel. Crops have been modified to resist the herbicides that destroy broad-leaved plants, including milkweed. Butterflies arriving in this area find no nectar plants and no milkweed to nourish the generation that returns to Mexico. With fewer monarchs making the return migration, even fewer find their way to the East Coast the following year.
Did we see lots of monarchs last year? Returning north, butterflies depend upon reliable and frequent sources of nectar, principally from masses of blooming flowers in their migratory pathway. They are not picky about their nectar sources, feeding on a wide variety of flowers, of many colors. While some butterflies prefer red, purple and pink, they perceive ultraviolet light, so a yellow flower may have a pattern recognized by insects but unseen by us, according to Hamilton.
“Butterflies are nearsighted, so large masses of flowers will attract them, with the same type of flower in a grouping,” she says.
Asters, black-eyed susans and tickseeds pack flowers into a central disk, where insects can collect nectar without expending a lot of energy. With a long proboscis acting as a soda straw, butterflies can suck nectar from flowers with long tubes such as cardinal flower, wild bergamot and field thistle, according to Hamilton.
Many gardeners prize nonnative reseeding butterfly bush and lantana for flowers that attract butterflies, but the shrubs are listed as invasive or weedy in some areas.
Monarch butterfly populations are seriously stressed, from habitat destruction, loss of nectar flowers and milkweed plants, and several years of unusual weather patterns.
How you can help
Plant milkweeds: Create Monarch Waystations in home gardens, at schools, businesses, parks, zoos, nature centers, along roadsides, and on other unused plots of land.
Provide nectar plants -- goldenrods, joe pye weeds, cardinal flowers, asters.
Join the citizen science group that reports sightings of monarchs on a daily basis (www.journeynorth.org).
Avoid pesticides, and limit mowing of natural areas, especially those where milkweeds grow.