Eastern Tiger Swallowtail butterfly (Papilio glaucus) is one of the most familiar butterflies in the eastern United States. The male is yellow with four black "tiger stripes" on each fore wing. Females may be either yellow or black, making them dimorphic. The yellow morph is similar to the male, but with a conspicuous band of blue spots along the hindwing. When basking in the sun, their outspread wings can be 3 to 5.5 inches from tip to tip.
Although they are solitary creatures, often flying high in the treetops, you can sometimes spot a special sight when a group of swallowtail males is “puddling.” Male butterflies come together at damp places in the soil and drink water. The water contains sodium ions and various amino acids, which appear to allow them to live longer. Adults of both sexes take nectar from a wide variety of native and exotic garden plants.
Females lay their large green eggs singly on plants in the Magnolia and rose families. Common host plants include tulip tree and wild black cherry and sweet bay Magnolia.
Eastern Tiger Swallowtail caterpillars are brown and white and resemble bird droppings. Later, as they mature, the caterpillars turn bright green and have two amazing black, yellow, and blue false eyespots on the thorax above and behind their true eyes to make it look like a snake’s head with glaring eyes a nose and mouth! Presumably, birds and other potential predators are put off by this impressive “snake in caterpillar’s clothing” mimetic display and the swallowtail is spared. If touched or pecked by a lizard, bird, or inquisitive human, the larvae evert a set of bright orange glands (the osmeteria) from the neck region. These produce a foul-smelling blend of defensive acid secretions that are wiped onto the attacking animal.
US Forest Service http://www.fs.fed.us/TigerSwallowtail.shtml