Press-Republican

June 9, 2013

Tiger Swallowtails back to fly into face of danger

By Elizabeth Lee
Press-Republican

---- — It’s early June and the Tiger Swallowtails have reappeared. They seem to appear from thin air in the most unlikely places.

Since I was a child I’ve always imagined they carry secret messages. Their large size, bright colors and twitchy flight pattern make them seem as musical as birds but it’s their silence that exaggerates the surprise of seeing one.

The Tiger Swallowtails are already well along in the business of mating and producing two or three generations before the end of summer. Unlike the Monarchs that return from exotic places in Mexico, the Tiger Swallowtails stay in northern forests in winter. In the fall, each caterpillar will form a hard chrysalis that it will hang from a twig, branch, roof, swing set or other surface by a thread-like attachment. In the chrysalis they transform again and in spring emerge as adults. The adult butterfly will live 3 to 4 weeks if it doesn’t succumb to predators.

Butterfly wings are truly spectacular inventions of nature. Although they grow in two pairs, the fore and hind wing on each side become attached during flight and function as one wing.

The wings are formed of thin, almost transparent membranes made of chitin, like human hair and fingernails. Over the membranes thin scales form.

The website science.howstuffworks.com explains, “Besides being responsible for the magnificent colors characteristic of butterflies, scales also protect and insulate the insects and aid in the flow of air along their wings as they fly. Scales also may help the butterfly to soak up the heat that flying requires.”

Special scent scales of male butterflies emit pheromones that attract females.

Survival for all butterflies is tough and bad weather makes it tougher.

Before the weather forecast is even announced, butterflies face a high mortality rate because so many predators feed on them. Predators include birds, rodents, reptiles, amphibians, viruses and even other parasitic insects. Despite the odds, Tiger Swallowtails are not considered threatened as a species.

Like other insects, butterflies are cold-blooded. They need sun to warm their muscles enough to move their wings so they can fly to food sources. When the temperature drops or the sky is cloudy, they can be forced to stay still.

In an article in Scientific American in 2006, Michael Raupp, professor of entomology at the University of Maryland, put raindrops into perspective.

“Suddenly, a fast-moving thunderstorm approaches, bringing gusty winds and large raindrops. For the monarch and other butterflies this is not a trivial matter. An average monarch weighs roughly 500 milligrams; large raindrops have a mass of 70 milligrams or more. A raindrop this size striking a (butterly) would be equivalent to you or I being pelted by water balloons with twice the mass of bowling balls.”

Tiger Swallowtail caterpillars eat a variety of host plants, preferring wild cherry and tulip trees. Adult butterflies feed on the nectar of wild plants and garden flowers. Many garden centers and nurseries sell native plants that our native Tiger Swallowtails like.

Female Tiger Swallowtails can look like the bright yellow males but also can have a dark color, mimicking other kinds of Swallowtails. Male Tiger Swallowtails have an odd habit called “puddling,” when a group crowds around damp gravel or a puddle.

Scientists have found that the puddling butterflies are commonly newly emerged males extracting nutrients that may help them develop.

Elizabeth Lee is a licensed guide who lives in Westport. She leads recreational and educational programs focused in the Champlain Valley throughout the year. Contact her at lakeside5047@gmail.com.