In adults, the upper surface of the forewing is mostly black, with ivory spots along the bottom margin. The upper surface of the hindwing has an orange spot on the costal margin which is unique to spicebush swallowtails. There is also a band of bluish (female) or bluish-green (male) scales on the upper surface of the hindwing. The bottom margin of the hindwing has bluish or ivory spots, and also a “tail” measuring 9 to 12 mm long at the bottom of the wing. This feature is similar to other swallowtails such as black swallowtails (Papilio asterius) and pipevine swallowtails (Battus philenor). However, the "tail" in P. troilus is broader and spatulate. Wingspan ranges from 80 to 115 mm.
The larval or caterpillar form initially resembles bird droppings, but in later instars is green with a pale yellow lateral line running the length of the caterpillar. The underside of the caterpillar is pinkish-brown, and each abdominal segment is ringed by six blue spots outlined in black. One dot on each side is below the yellow lateral line.
Caterpillars have two pairs of false eyespots: one pair is toward the back of the thorax, and is small and yellow. The other pair is closer to the head, and is yellow with a black spot in the middle, and a white spot that resembles the glare off a black eye. The combination of the eyespots and a swollen thorax is believed to be a mimicry of either green snakes or tree frogs.
Female caterpillars are often slightly longer than males. Pupae can be brown or green depending on the season, mimicking leaves of spring and fall, and have a pair of horns at the top of the pupa. (Allen, 1997; Hall and Butler, 2000; Jaques and Sexton, 2004; Nitao, et al., 1991; Saunders, 1932; Struttman, 2004; Tyler, 1975)
Spicebush swallowtails (Papilio troilus) are found in eastern North America from southern Canada to Florida, and west to Oklahoma, Manitoba, and central Texas. This species is less common on the western edge of its range, along the southern Mississippi River, as well as in New England. Occasionally these butterflies are found as far west as Colorado, and as far south as Cuba. (Hall and Butler, 2000; Jaques and Sexton, 2004; Struttman, 2004; Tyler, 1975; Hall and Butler, 2000; Jaques and Sexton, 2004; Struttman, 2004; Tyler, 1975)
The larval form of P. troilus is found in deciduous woodlands, wooded swamps, and pine barrens. The adult form is a fairly common butterfly within its range, that can be seen in woodlands, parks, yards, fields, and roadsides, but prefers the borders of shady woods. Males are often found near moist, sandy areas along roads or streams. (Allen, 1997; Hall and Butler, 2000; Jaques and Sexton, 2004; Struttman, 2004; Tyler, 1975)
Spicebush swallowtails lay their eggs on the undersides of leaves. Larvae hatch and initially resemble bird droppings, but come to mimic a snake, complete with eyespots, in later instars. These larvae form pupae which are green (summer) or brown (fall) and metamorphose into butterflies. Some pupae hibernate over winter, and these are usually brown to mimic dead leaves. Shorter photoperiods associated with the coming of winter trigger pupae to assume the brown color, regardless of whether the leaf they live on is green or brown.
In order to find females, males patrol flyways on hilltops or host plant sites. When patrolling males meet, they generally fly in opposite directions. Females have much lower representations in these areas. The only areas of equal representation are nectar sources. When a female appears, a male flies towards her and performs a brief courtship ritual, lasting less than a minute. If the female is receptive to the courtship, copulation occurs, often lasting over an hour. Both males and females often copulate with multiple partners. A fertilized female oviposits in the warm portion of the day, laying eggs singly on young host leaves. (Allen, 1997; Lederhouse, 1995)
Spicebush swallowtails breed after becoming adults. This takes place during the summer months (April to October, or March to December in the southern part of the range) when there is ample food for the larvae. Though both males and females copulate with multiple partners, females are increasingly less likely to seek another mate with each successful copulation. Females search out host plants by visual and chemical cues, then land on a plant and drum the leaf with their forelegs to "taste" it, and confirm it as a host plant. (Lederhouse, 1995; Nishida, 1995; Struttman, 2004)
Care of eggs once they are laid, or of larvae, does not occur in this species. However, females do invest in their young by producing nutrient rich eggs to allow the larvae to develop until hatching. They also select host plants carefully, to help ensure the survival of their young. (Hall and Butler, 2000)
Adult swallowtail butterflies live roughly from 2 days to 2 weeks. (Lederhouse, 1995)
Caterpillars of P. troilus form a shelter out of a leaf by folding it over and spinning silk to form a nest inside the leaf. They feed nocturnally, and when disturbed, an orange scent gland behind their head releases a disagreeable odor. When the caterpillar completes its development, it pupates and becomes a chrysalis, before metamorphosing into a butterfly.
As adults, the butterflies fly around in search of mates and nectar. Adult males engage in a common practice among swallowtails called "puddling". They may congregate around moist, sandy areas along roads or streams, and sip moisture and minerals from the soil. (Allen, 1997; Bouseman and Sternburg, 2001; Hall and Butler, 2000; Jaques and Sexton, 2004; Struttman, 2004)
Larvae are confined to the plant that their egg was laid on. Adults do not define a home range. They simply fly around in search of nectar and mates. (Hall and Butler, 2000; Jaques and Sexton, 2004; Struttman, 2004)
Females use both visual and chemical cues when finding hosts plants on which to oviposit. After landing on a plant, a female confirms the plant as a host plant by drumming the surface of the leaf with her forelegs, which have contact chemorecepters located on the foretarsi.
Information on communication between individuals is limited to mating contexts. Males apparently recognize females visually. The courtship display of a male involves many visual elements. In additon, during the process of mating itself, there is some contact, probably relaying information between the individuals. (Feeny, 1995; Nishida, 1995)
As in many animals that undergo metamorphosis, the diet of the young differs from the diet of the adult.
In P. troilus, larvae feed on the leaves of aromatic trees and shrubs in the family Lauraceae. Their primary hosts are spicebush (Lindera benzoin), sassafras (Sassafras albidum), but they are also known to feed on camphor (Cinnamomum camphora) sweetbay (Magnolia virginiana), and redbay (Persea borbonia). The choice of host plant depends primarily on host availability in a particular part of the range. There is evidence of geographic divergence among populations with larval adaptation to the most common host species.
Adult P. troilus butterflies feed on nectar, and are partial to honeysuckle, clover, and thistle flowers. Their unusually long proboscis allows them to reach nectar in unusually deep flowers such as bee balm. They will also drink nectar from other flowers such as jewelweed, milkweed, azalea, dogbane, mimosa, and sweet pepperbush. (Allen, 1997; Hall and Butler, 2000; Jaques and Sexton, 2004; Nitao, et al., 1991; Saunders, 1932; Struttman, 2004; Tyler, 1975)
Although spicebush swallowtails employ extensive mimicry throughout their lifecycles, mimicking bird droppings and green snakes as caterpillars, and mimicking the poisonous pipevine swallowtail (Battus philenor) as adults, they suffer from extensive predation. Spiders, insect predators such as dragonflies and robber flies, and especially birds, will eat swallowtail butterfly adults and larvae. (Newton, 2004)
Spicebush swallowtail larvae are specialist herbivores, feeding on members of the family Lauraceae. Adults are generic pollinators for many flowers, inadvertently pollinating while feeding on nectar. (Hall and Butler, 2000; Struttman, 2004; Tyler, 1975)
Spicebush swallowtails are not usually considered pests, though their host trees occasionally suffer slightly when planted as ornamentals. (Newton, 2004)
Swallowtail butterflies have a slow and lazy flight, and because of this, they are easy to catch, making them prime collector's items. They are also popular photography subjects because of their large size, showiness, and slow flight. Since spicebush swallowtails are generic pollinators, they are also beneficial to crops. (Newton, 2004)
The Nature Conservancy ranks spicebush swallowtails as a G5 species, which means that they are in no danger on a global scale, though may be quite rare in parts of the species' range, especially on the periphery. (Struttman, 2004)
A subspecies of Papilio troilus, called Papilio troilus ilioneus, is the dominant type of this butterfly in Florida. The major distinguishing feature of this subspecies is that it has enlarged, light submarginal spots. (Harris, 1972)
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