Ninety-five percent of butterflies are not pollinators,“ according to lepidopterist Liam O'Brien. Instead, most pollination is accomplished by bees, wasps, flies, and moths. The butterflies are ”food for everyone else“: a ”moving smorgasbord.“
O'Brien talked about gardening for butterflies at a recent talk sponsored by the Loma Prieta chapter of the Sierra Club. He encouraged everyone to learn butterflies. San Francisco, he said, has 34 breeding species of butterflies (versus about 200 bird species), and it's possible to learn them all. The peninsula has mostly the same butterflies, he said. O'Brien is also an illustrator and has produced a fold-out brochure entitled Butterflies of San Francisco with life-size images of all the species found here. Most of the butterflies are surprisingly small, an inch or less across.
Eighty percent of all butterflies are eaten by birds, O'Brien said. A female butterfly lives for about 10-15 days. About 80 percent of the eggs she lays are eaten. Of the remaining eggs that become caterpillars or pupae, 80 percent are parasitized by native wasps and flies.
In a recent New York Times piece, entomologist Douglas Tallamy noted that it takes 6,000 to 9,000 caterpillars to raise a clutch of chickadees. For the 16-18 days it takes for chicks to fledge, the parent chickadees bring a caterpillar to the nest every 3 minutes for 14 hours a day, starting at 6 in the morning.
Butterflies are specialists when it comes to laying eggs and generalists when it comes to nectaring, O'Brien said. That is, each species of butterfly requires specific host plants (species or plant family), which the caterpillars will feed on when they hatch. For instance, California pipevine is the host plant of the Pipevine Swallowtail butterfly. This species ”can get very far into urban corridors,“ he said, so ”you can really help“ by planting its host plant. (Be patient: I've heard it can take a couple years for a butterfly to find a particular plant.) The Anise Swallowtail lays eggs on plants in the carrot family, nonnative fennel being the most common host.
Planting 5 or 6 plants will give you ”uber-bang for your buck,“ O'Brien said. California buckeye trees are ”the gas station of all butterflies,“ though only the Echo Blue lays its eggs there. He also singled out buckwheats and native asters as exceptional nectar plants.
The Western Tiger Swallowtail uses willow and sycamore trees as host plants, and patrols ”long linear concourses“ such as rivers or, in the city, Market Street, which is lined with sycamores. Other large butterflies that use trees as host plants include the California Sister (oaks) and the Mourning Cloak (willows).
The Monarch is the ”gateway butterfly for most kids,“ O'Brien said. But ”we treat them as objects, not wildlife“ when they are released en masse at parties. They're not ”party favors." It would be ridiculous to treat any other animal this way, he said. He also cautioned against planting tropical species of milkweed for Monarchs, because year-round blooms may encourage the butterflies to lay eggs at the wrong time of year or to linger instead of migrating. Both problems harm the health of the species.
Skippers are fairly common butterflies, but they are small! This one is a little more than an inch long. The host plant for the Fiery Skipper is bermuda grass!
Detail from an illustration by Liam O'Brien from the Butterflies in San Francisco brochure, copyright 2009 Nature in the City.
Weedy areas in your yard may help butterflies. The Red Admiral butterfly uses stinging nettles as a host plant.
© 2015 Tanya Kucak