Windshield splat attack

Every fall hundreds of thousands of monarch butterflies flee the frosty foothills of Utah, Wyoming, Montana and southern Canada for the warmth of eucalyptus groves along California’s central and southern coast. The orange masses draw thousands of humans to events such as Sunday’s Welcome Back Monarchs Day at Natural Bridges State Park in Santa Cruz. Docents can tell you almost anything you want to know about these monarchs: that they travel up to 2,000 miles at speeds of up to 30 mph; that they lay their eggs on toxic milkweed pods, which render their offspring poisonous to predators; that they return annually to the same groves in 300 sites from Baja California to Sonoma County. What the docents can’t tell you is how the monarchs know to make the journey. Researchers believe the migration may be a light-triggered response, possibly associated with directional crystals deep in the insect’s brain. On the spring equinox, the monarchs begin their trip to summer homes in the mountains. Exactly 180 days later on the fall equinox, they begin their return trip to winter digs along the coast. Because the journey is long and the butterflies’ life span short, this year’s travelers will be the great- and great-great-grandchildren of the butterflies that came last year. “The ones who find their way to the overwintering sites have never been there before and yet they visit the same trees,” says Lincoln Brower, a biology professor at Sweet Briar College in Virginia, who has studied monarchs for 50 years. “Miraculous? I’d have to say yes.” For monarch-watching sites, go to www.monarchwatch.org/download/pdf/where.pdf. For Natural Bridges State Beach, call (831) 423-4609.

-- Veronique de Turenne