There’s a new bug in the garden, and it looks a lot like bird poop. Unappetizing, you bet, but so clever: This odd little caterpillar’s job is to avoid being eaten, and one day -- like magic -- become a giant swallowtail butterfly.
Even in one of the driest years on record and an “awful” one for butterflies, according to Fred Heath, author of “An Introduction to Southern California Butterflies,” giant swallowtails are fairly easy to spot, particularly in neighborhoods where citrus is common.
“Because it feeds on evergreen trees,” says Brent Karner, associate manager of entomological exhibits at the Natural History Museum of Los Angeles County, “it’s not as dependent on rainfall as other species. It’s one of the few butterflies we’ve seen right through this dry year.”
The giant swallowtail, once rare in these parts, is now well-established in Southern California. Its funny-looking larvae, known as “orange dogs,” feed on citrus and other members of the rue family. But gardeners needn’t worry, and wild lands aren’t threatened.
Orange dogs dine singly, not in packs, and do minimal damage to mature citrus trees. Native-plant specialists haven’t seen them in the wild, where larval food plants are virtually nonexistent.
Butterfly enthusiast Bruce Steele is thrilled that giant swallowtails have at last found his oak-shaded Altadena garden. He darts among trees, searching for giant swallowtail eggs (minuscule) and caterpillars -- some smaller than rice grains -- on odorous rue plants that he grew solely to attract egg-laying adults.
“I had a book about them when I was a child,” he says. “I guess I’m still a kid at heart.”
The giant swallowtail butterfly, Heraclides (Papilio) cresphontes, is native to the Southeast. Since the 1960s, populations have spread west following a corridor of suburban development and the species’ favorite larval food source -- citrus -- through Arizona, into the Imperial Valley, then San Diego and north to Orange and Los Angeles counties. They’ve been sighted as far north as Santa Barbara and Bakersfield.
Numbers have surged since 2000, says Jess Morton, president of the Palos Verdes-South Bay chapter of the Audubon Society. Members have held a butterfly count at the same location, on the first Sunday in July, every year since 1991. According to their records, a single giant swallowtail was first seen in the South Bay in 2000. They counted 23 in 2007.
Giant swallowtails are hard to miss. They’re powerful fliers. With a wingspan of 5 to 6 inches, it’s the largest butterfly in North America, bigger than a monarch and larger than many birds.
The wing tops are velvety brown, almost black, with garlands of yellow and a blood-red blotch near each elegant, yellow-filled tail. The rarely seen undersides are mostly yellow with brown and cream. The body is furry and gilded, the head black with yellow racing stripes.
“It’s a beautiful butterfly and lovely to look at,” says Arcadia entomologist Steven R. Kutcher. “But what’s more exciting is to listen to it fly.” He describes the sound of the wing beats as rhythmic, soft and whooshing.
Elaine Fresco, who has had a garden in Laurel Canyon for 30 years, saw her first giant swallowtail this August.
“It was huge,” she says. “At first I thought it was a hummingbird.”
Then there were two, and Fresco, a certified nurse-midwife, watched in awe as the butterflies laid tiny yellowish eggs on the leaves of her grapefruit and white sapote trees.
“Females are quite selective about where they oviposit,” says Jack Levy, a Pasadena butterfly expert and conservationist. Giant swallowtail eggs are laid on very new growth and leaf tips -- tender tissues, just right for tiny, chewing mouthparts.
The change from egg to butterfly involves a process called complete metamorphosis. It’s a wonder of nature in four stages: egg, larva, pupa and adult.
In this climate, giant swallowtail eggs hatch in days to a week. The larvae, or caterpillars, experience five growth spurts called instars, each lasting about a week. At the end of the fifth instar, each chubby bird poop finds a nice spot and encloses itself in a brownish chrysalis that mimics a dry, curled-up leaf. (By the way, moths make cocoons.)
Giant swallowtails will pupate anywhere, including fences and walls.
“The larvae can go great distances, walking long ways to pupate someplace different,” says the museum’s Karner. He’s seen them crawl across the butterfly pavilion, a distance of 75 feet.
After three weeks, the once-homely youngster emerges as an adult butterfly, a magnificent creature that eats, drinks, mates, lays eggs and dies in about two weeks.
One female can lay hundreds of eggs, and her hatchlings face many challenges. Some are consumed by wasps and flies. Fortunately, birds find the larvae distasteful. Ants and other small predators are repelled by the caterpillar’s secret weapon: a fleshy, bright orange osmeterium that pops up from the larva’s head and emits a foul odor likened to rancid butter.
“These animals are fun,” Morton of the Audubon Society says. “You don’t have to hunt for this insect. These butterflies come to you; just plant an orange tree.” (For the record, an orange dog reared itself on Morton’s lemon tree.) In fact, any citrus will do.
You can also plant white sapote (Casimiroa edulis, a delicious tropical fruit tree) or rue (Ruta graveolens, available in nursery herb sections) to attract egg-laying females.
Though particular about where they lay their eggs, giant swallowtails will sip nectar from many different flowering plants. They prefer long tubular flowers (blossoms also liked by hummingbirds), but they’ve been seen on bougainvillea, buddleja, caesalpinia, cestrum, gaillardia, tithonia and zinnia.
Levy reminds beginners that to have butterflies, you need two types of plants: larval food plants for hungry caterpillars and nectar sources for adult butterflies. The latter will add color and beauty to your landscape; the former are going to be eaten.
Though backyard trees are prime targets, University of California farm advisors and citrus specialists do not expect this elegant new resident will be a problem. Even in their native Florida and south Texas, where they are abundant, the giant swallowtail is a minor pest to orchards.
So don’t be alarmed if you discover an orange dog munching on your citrus leaves. It won’t bite you. Resist the urge to squish or spray it.
David Kellum, entomologist with San Diego County’s Agricultural Commissioner’s Office, hopes gardeners will nurture giant swallowtails and their larvae. “Bird-dropping caterpillars” brought into his office by homeowners are swiftly relocated to citrus trees at Quail Botanical Gardens in Encinitas.
Steele is adding more rue this fall so that more giant swallowtails will visit his garden. He calls his experience a “great joy.” He sometimes takes a well-developed caterpillar to the office on a Monday. By Friday, it has formed a chrysalis, to the astonishment of his co-workers.
“Once the connection is made,” Steele says, “your world opens up.”
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Where to find them
In Southern California, giant swallowtails are active all year. Watch for them in flight late morning on clear sunny days. Here are other ways to catch a glimpse of the butterflies:
Watch: On YouTube, video of a giant swallowtail caterpillar hatching -- then devouring its egg case. www.youtube.com/watch ?v=y_7A9ZSr-zY.
Read: “An Introduction to Southern California Butterflies” by Fred Heath with photography by Herbert Clarke, and “Butterflies Through Binoculars: The West, a Field Guide to the Butterflies of Western North America” by Jeffrey Glassberg
Information: North American Butterfly Assn., Los Angeles area ( www.naba.org/chapters /nabala/index.htm) and Orange County ( www.naba.org/chapters/nabaoc/index.html)