Papilio glaucus

by Nicole S. Davis

 The Eastern Tiger Swallowtail or the Tiger Swallowtail is a very interesting animal. Its formal name is Papilio glaucus. It belongs to the Phylum Arthropoda, the Class Insecta, the Order Lepidoptera (Butterflies and Moths), and the Family Papilionidae (Swallowtails). Members of this family are the largest butterflies in the world. Strangely they only have a few wingbeats per second but fly very fast.

The eggs of the Eastern Tiger Swallowtail are green and then greenish-yellow with red spots. The larvae are very interesting. The younger larvae are dark and resemble bird droppings, but as they age they become green with a swollen thorax and a horizontal band of faint blue dots on each abdominal segment. They also acquire a black horizontal stripe edged with yellow between the first and second abdominal segment on the side closest to the head. They have a single pair of false eyespots on their middle segments that are yellow and ringed with black. This change plays a part in protection, which is explained later. The adults are very beautiful. They have a 7.9-14 cm wingspread range. The most common ones are yellow with four black bands on the front wings. The innermost band connects with the median band of the hind wing. The wing margins are black with a row of yellow spots. In the North most females are mostly black with a marginal row of yellow spots. The most beautiful part of their wings is the black-powdery blue on the hind wing divided by a wavy black band.

These butterflies have a wide range. They are seen all over North America. They tend to live in deciduous woodlands, especially woodland edges and wooded watercourses. This is where the males patrol all day to seek females. They are commonly found in gardens because they feed from flowers. The larvae commonly feed on several families of dicotyledons like magnolia, sweetbay, birch, cottonwood, mountain ash and willow. The adults sip flower nectar, and carrion juices. Their major foodplant is the wild black cherry and the tulip tree. They are fond of aromatic lilies.

The larvae are better at protecting themselves than the adults probably because the larvae can't fly away from predators. They resemble snakes with their large eyespots and their enlarged thorax. They also have an orange osmeterium, a forked, foul-smelling "snake-tongue" gland that pops out behind the head to repel ants and other predators. The black swallowtails are better protected than the yellow swallowtails. Research has shown that black swallowtails are thought to mimic the poisonous Battus Philenor or the Pipevine Swallowtail, which discourages birds from attacking. The irony of this is that while the black form benefits from mimicry, the males prefer the yellow female.

In courtship the male and female flutter about each other before landing and mating. If they feel threatened while mating the female carries the male away. Male swallowtails have a perfume like pheromone that is used in courtship.

Unlike most butterflies the Eastern Tiger Swallowtail spreads its wings when resting or basking and they are even more unusual in the fact that they continue to flutter their wings while feeding on nectar. This is one of the most common and conspicuous butterflies of the Eastern United States. Because of this, in 1991, it was adopted as the Virginia State Butterfly.

Written fall 2000, as a service learning project for Dr. Gary Coté's Biology 102 class at Radford University. Copyright Pathways for Radford.