When giant swallowtails are caterpillars, they are commonly known as "orange dogs." These butterflies receive this nickname since they primarily eat orange tree leaves. Sweet orange tree agriculturists consider these caterpillars minor pests. Giant swallowtail caterpillars also consume leaves on citrus trees such as the lime pricklyash, Mexican orange, sea torchwood, hoptree and the Hercules-club. These caterpillars also eat leaves on gasplant and white sapote plants. During their larval stage, giant swallowtails use toxins from leaves they eat to defend themselves from insect parasites and birds.
When giant swallowtails reach adulthood, their diet changes from citrus leaves to flower nectar. These butterflies obtain nectar from flowers such as azaleas, goldenrods, swamp milkweeds, Japanese honeysuckles and bougainvilleas. Liquids from animal manure is another source of nourishment for giant swallowtails.
Giant swallowtails are abundant in U.S. regions such as the East Coast, Midwest and Southeast. However, these butterflies are scarce west of the Rocky Mountains. Outside of the United States, giant swallowtails are seen in South America, Bermuda and Canada. The primary habitats for adult giant swallowtails are pine forests and gardens with flowers; many specimens fly to man-made butterfly gardens where flowers are plentiful. Adult giant swallowtails also fly to citrus groves to lay their eggs since these insects dine on citrus tree leaves in their larval stages.
Larval giant swallowtails cause minor damage to citrus tree leaves and stems. While the giant swallowtail caterpillars are considered minor citrus tree pests, most agriculturalists do not spend enormous amounts of time or money trying to rid their orchards of these caterpillars. The University of Florida IFAS Extension recommends simply hand-picking giant swallowtail caterpillars off leaves if an agriculturalists wants it removed. The university also states mature citrus trees can withstand damage caused by giant swallowtails.
The giant swallowtail has several relatives in the United States with similar eating habits. Among the giant swallowtail's relatives are the tiger swallowtail -- a black and yellow species -- the black-and-blue spicebush swallowtail, palamedes swallowtail and two-tailed swallowtail. When they are caterpillars, these butterflies eat tree and brush leaves, similarly to the giant swallowtails. Adult swallowtails feed on nectar. The giant swallowtail is the largest of the U.S. swallowtail butterflies.