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January 6, 2004 > In Search of Danaus plexippus

In Search of Danaus plexippus

The Mighty and Mysterious Monarch Butterfly Visits Ardenwood

Walking through wet grasses on a chilly morning at Ardenwood Historic Farm in Fremont, Naturalist, Tara Reinertson, was doubtful that we would get a clear view of thousands of Monarch Butterflies roosting in the Eucalyptus grove. But, optimistically, we pressed on. Long rows of leaves, on closer inspection, turned out to be huddled masses of Monarchs who were braving the cold weather too. The dull underside of their wings belied bright orange patterns on the top surface when stretched out in less inclement weather. A large migration target for Monarchs from the Eastern portions of the United States and Canada is Central Mexico. It is said that in ancient Mexico, the Aztec believed Monarch butterflies were the incarnation of their fallen warriors wearing the colors of battle.

Described as "Taxi Drivers for Pollen" by Tara, these butterflies not only make a miraculous annual journey of thousands of miles from summer habitat to "overwintering" sites, but do it without the benefit of a prior generation's guidance since each migration involves a different generation. Just as bees spread pollen, essential for many plants to create fruit and reproduce by moving from flower to flower in search of nectar, so do butterflies - thus the taxi driver reference. Ardenwood is just one small site that attracts Monarchs Butterflies due to a mild winter climate and proximity to milkweed plants. This quirky denizen of the animal kingdom not only goes through a complex series of appearances (metamorphosis) during its life - Egg, Caterpillar (larva), Crysalis (pupa), Butterfly (adult) - milkweed is its sole diet during the caterpillar life stage. This preference keeps milkweed plants, which grow "like a weed," in balance, and protects adult butterflies who incorporate milkweed poisons in their body without harm to themselves.. Birds and other predators quickly learn that the bright colors of the monarch caterpillars and butterflies are warnings of sickness and even death, if ingested.

Following a Monarch throughout its life, researchers have determined that female butterflies lay their eggs, usually one at a time, to the underside of a milkweed leaf. An average female may lay over 100 eggs, with a purported record of 1179! When the new generation is hatched, they start their lives as caterpillars, voracious "eating machines" consuming a strict milkweed diet. After growing up to 3,000 times larger - if a human baby did this, it would end up the size of a Blue Whale at two weeks of age - the gorged caterpillar curls up, attaches itself to a sheltered spot, sheds its old skin and creates a case called "chrysalis." Within the chrysalis, the caterpillar body dissolves and is recreated as a butterfly in 10 to 15 days. A fully formed butterfly emerges for the remainder of the life cycle. It takes about a month to go through the stages from egg to adult. Adults in the summer generations only live a few weeks while the winter generation, with the additional chore of migration, may live up to nine months. It is the sons and daughters of overwintering butterflies that begin the reverse migration to summer locations. After three more cycles, the fifth generation of Monarch Butterflies will sense shorter days and cooler nights. These great-great grandchildren of the butterflies now inhabiting the local Eucalyptus grove will travel back to Ardenwood in the next fall migration!

If you would like to visit the Monarchs at Ardenwood, there is still time before the next generation begins moving north. Weather permitting, Monarch Butterfly walks are held every Saturday and Sunday in January at 11 a.m. and 2 p.m. A slide show about these incredible animals will be held in advance of a butterfly walk, at 12 noon and 1 p.m. on January 11, 17, 25, 31 and February 1 & 8. Additional activities are planed throughout January and February.

A "Farewell to Butterflies Celebration" will be held at Ardenwood Historic Farm on Sunday, February 15 from 1 p.m. to 3 p.m. Activities include butterfly crafts and a parade (bring your own wings) and planting of milkweed in honor of the Monarch Butterfly.

For more information, contact Ardenwood Historic Farm, 34600 Ardenwood Blvd., Fremont (510) 796-0663 or or visit Coyote Hills Regional Park, 8000 Patterson Ranch Rd., Fremont also has a butterfly garden and vivarium (510) 795-9385 or Another butterfly garden can be found at Shinn Park, 1251 Peralta Blvd., Fremont; (510) 795-0891, (510) 790-5540 or call Rod or Eva Ricciarelli (510) 656-7702.

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