FROM THE NEWS-LEDGER — APRIL 3, 2013 –
By Mary K. Hanson, Tuleyome Association –
It’s usually in March and April when these butterflies first emerge from their chrysalises and set out to feed on nectar and find suitable mates. I look for them along the riverbanks and streams I visit in the spring, knowing I’ll find them on the plant for which they’re named. I love their velvety black wings with their bright blue iridescence that winks in the sunlight as the butterflies do their early morning warm-up flights.
They really are one of the most recognizable butterflies in the region. When viewed from the top they are predominantly black with an iridescent blue sheen on their hind wings (which is brighter on the males than it is on the females) and white spots along the wing margins. The underside of their wings boasts some bright orange spots surrounded by black and iridescent blue. Can you name my favorite butterfly?
It is the Pipevine Swallowtail (Battus philenor)!
The Pipevine Swallowtail’s body is fuzzy black with white spots. Its long curling proboscis is used to feed on nectar from a variety of flowers and thistles, but the butterfly gets its name from the host plant on which it lays its tiny reddish-brown eggs: the California Pipevine, also known as the California Dutchman’s Pipe (Aristolochia californica). The flowers, which look like fat pitchers or calabash pipes, arrive just before the vines start sprouting their broad vaguely heart-shaped leaves. Although the flowers look like those of some insectivorous (insect-eating) plants, the Pipevine isn’t an insect-eater. Later in the season, when the flowers drop off, they are replaced by six-winged ribbed seed pods.
These vines can be found growing naturally in riparian zones (moist areas where forests meet streams and rivers) throughout the northern and central parts of the state, including the Sacramento Valley, Yolo County and Napa County. Although they are not considered endangered, there are some areas where the vines have been exterminated as weeds or nuisance plants by those who do not recognize them or understand their importance to the local ecology. And that is very bad news for the Pipevine Swallowtails. The female butterflies will only lay their eggs on the vines; and when the caterpillars emerge, they feed exclusively on the Pipevine. No other plant will do. So, where the Pipevines are destroyed, so are the Pipevine Swallowtails.
The caterpillars forage in groups when they’re young and then become more solitary as they age. They go through stages called “instars” during which the caterpillar sheds its old skin, sort of like a snake, and emerges larger and darker. The caterpillars, like the adult butterflies, are very recognizable. They usually appear locally in April and May (but may be seen as late as September) gorging on the leaves, stems and pods of the Pipevine plants. When newly hatched, the caterpillars are reddish-brown. As they grow in girth and length, they then darken to a deep rich black with bright red-orange spines down their backs. This black-and-red coloring mimics many species that are toxic or unpalatable to predators and this helps protects the Pipevine Swallowtails. The vines and pods that the caterpillars eat contain a substance called aristolochic acid which is passed on to the caterpillars and is also carried in the bodies of the adult butterflies. As additionally frightening deterrent, when aggravated the Pipevine Swallowtail caterpillar rears up and disgorges bright orange “horns” from the top of its head which are slimed in toxic goo.
In May or June, the fully grown caterpillars start to hang themselves from the side of trees, fence posts, twigs or branches from silken threads they weave called “suspension loops”, and then form a chrysalis around their torpid bodies. The chrysalises are usually brown, but can also be golden-brown or green when they’re first made. When you find them, look closely at these tiny delicate works of art. They have points and whorls, and an almost stained-glass-window quality to their architecture. These special cases protect the metamorphosing caterpillars through the end year and into the next spring, when they will emerge again as butterflies.
Resist the urge to touch them. To ensure that this intricate, complex, and beautiful cycle of life continues, it is essential to leave the eggs, caterpillars and their chrysalises wherever you find them. Taking photographs is the best way to “take them home with you”. There is a saying: “When you teach a child not to kill a caterpillar, you do as much good for the child as you do for the caterpillar.” (Okay I made that up, but you get the point.) It’s also essential that the habitat where the native Pipevines grow is protected – and that’s where you can make the greatest impact on behalf of these butterflies. Remember that riparian zones are actually vital ecosystems that contain and support many tiny miracles – like the Pipevine Swallowtails – which need and deserve your respect and protection. You can help safeguard the riparian zones in and around your community by supporting the efforts of your local conservation and environmental organizations. Volunteer. Donate your time and dollars when you can. Together we get things done.
Tuleyome Tales is a monthly publication of Tuleyome, conservation organization with offices in Woodland and Napa, CA. Mary K. Hanson is an amateur naturalist and photographer who is currently serves as Executive Assistant to Tuleyome’s Executive Director. For more information about Tuleyome, go to www.tuleyome.org.
Copyright News-Ledger 2013