The Giant Swallowtail is one of the largest butterflies in the United States (along with the Tiger Swallowtails). Giants can be easily identified, even in flight. Their large size is an obvious give away - about 6 inches from wing to wing. The top side of the wings are dark brown (almost black) with prominent yellow bands. As if that wasn't enough, they are yellow on the underside, which contrasts with the black topside. The broken pattern on the yellow underside of its wings helps conceal it from predators. From above, the Giant Swallowtail looks like dappled sunlight hitting a dark leaf. The hindwing has a red and black eyespot and a tail that is yellow near the tip. On the underside of the hindwing, there is a blue band and a small orange patch near the center.The sexes are similar, but the females are paler yellow and have a narrower yellow band at the base of the topside hindwing
Giant Swallowtails prefer open woodlands and fields, citrus groves, and gardens near woodlands. Their range is north to Virginia and Iowa, west to southern Arizona, south to the West Indies and northern South America. Normally a strong, high flier, the Giant Swallowtail is easily be enticed down to flowers, drink from them long and thirstily. They are especially fond of Butterfly Bush (Buddleia davidii) and Lantana (Lantana spp.). It also drinks from mud, fruit juices, and manure.
Eggs are large, round, and orange in color. Females lay eggs one or two at a time on the new growth. Young caterpillars eat only young, tender leaves and rest exposed on the upper leaf surfaces. Older caterpillars more often rest on twigs and branches.
The first three caterpillar stages are black and white and resemble bird droppings. The last two stages are brown with whitish patches on the tail end, around the middle and the sides of the front part of the body. Like other Swallowtails, these caterpillars have a bright red-orange forked organ (called an osmeterium) which emits a noxious odor. They stick out these scent horns to repel ants or other predators that might try to attack them.
The Giant Swallowtail caterpillars feed on leaves in the Rutaceae (citrus) family. They are called 'orange dogs' in south Florida, because of their love for Orange tree leaves. They're considered a minor agricultural pest down there. They will eat (in addition to cultivated citrus) many native citrus leaves: Wafer Ash or Hop Tree (Ptelea trifoliata), Torchwood (Amyris elemifera), wild lime or Prickly Ash (Zanthoxylum fagara), and Hercules-club (Zanthoxylum clava-herculis). I've raised them on Key Lime (citrus aurantifolia) leaves as well as Hercules Clubs. Also, they will consider Sweet orange (Citrus sinesis), Sour Orange (Citrus aurantium), Tangerine (Citrus reticulata), Grapefruit (Citrus mazima), and lemon (Citrus limon), Box Thorn (Severinia buxifolia), Rue (Ruta graveolens), and Trifoliate Orange (Poncirus trifoliata) which is used as a rootstock on which citrus is grafted. Females will lay on Nagami Kumquat (Fortunella margarita), but the larvae do not seem able to survive on this plant. Zanthoxylum spp. and Wafer Ash seem to be the preferred host plants.
The chrysalis is brown with dark markings and patches of green, resembling a piece of wood. The upper half is suspended by a silk girdle. The bottom is attached to a little silk button on a tree. The pupa (chrysalis) is the overwintering stage. BUT... they don't always overwinter!
A Giant Swallowtail (bottom) pupating right on top of a Black Swallowtail (top)
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