Spicebush Swallowtail (NPS Manassas National Battlefield Park Butterflies and Moths)

Spicebush Swallowtail

Papilio troilus

Summary ⁷

The Spicebush Swallowtail (Papilio troilus) is a common black swallowtail butterfly found in North America, also known as the Green-Clouded butterfly. It has two subspecies, Papilio troilus troilus and Papilio troilus ilioneus, the latter found mainly in the Florida peninsula. The spicebush swallowtail derives its name from its most common host plant, the spicebush, members of the genus Lindera.

Distribution ⁸

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.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

Morphology ⁹

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.

Range wingspan: 80 to 115 mm.

Average wingspan: 100 mm.

Sexual Dimorphism: female larger; sexes colored or patterned differently

Other Physical Features: ectothermic ; bilateral symmetry

Habitat ¹⁰

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.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Wetlands: marsh ; swamp ; bog

Other Habitat Features: urban ; suburban ; agricultural

Behaviour ¹¹

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.

Communication Channels: visual ; tactile ; chemical

Other Communication Modes: mimicry

Perception Channels: visual ; tactile ; chemical

Life cycle ¹²

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.

Papilio troilus produces two generations per year from April to October, except in Florida, where three are possible between March and December.

Development - Life Cycle: metamorphosis ; diapause

Reproduction ¹³

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.

Mating System: polygynandrous (promiscuous)

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.

Breeding interval: Males mate daily. A females may mate multiple times during her lifetime.

Breeding season: Breeding occurs between April and October.

Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous ; sperm-storing

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.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female)

Functional adaptation ¹⁴

Eye spots deter animals: spicebush swallowtail

Eyespots of the spicebush swallowtail butterfly caterpillar protect it from predators because their tear shape creates an illusion of movable, watchful eyes.
"The directionality of P. troilus's stare is achieved through a very simple design feature: the shape of the dark pupillary marking in the center of the eye. That marking, instead of being circular as it commonly is in actual eyes, is tear-shaped in the caterpillar's imitative version. It consists essentially of two portions: the basic circular marking, and a triangular anterior add-on that merges seamlessly with it. Leave out the add-on, and you have an eye with a circular pupil that is not nearly as able to convey the impression of looking forward or to the side." (Eisner 2003:96-97)
Learn more about this functional adaptation.

Conservation status ¹⁵

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.

US Federal List: no special status

CITES: no special status

Sources and Credits

(c) Lisa Brown, some rights reserved (CC BY-NC), http://www.flickr.com/photos/33695431@N00/2686733639
(c) 2011 Bill Stagnaro, some rights reserved (CC BY-SA), http://calphotos.berkeley.edu/cgi/img_query?seq_num=368509&one=T
(c) anonymous, some rights reserved (CC BY-NC-SA), http://images.dev.morphbank.net/?id=590029&imgType=jpg
(c) Museum of Comparative Zoology, Harvard University, some rights reserved (CC BY-NC-SA), https://mczbase.mcz.harvard.edu/specimen_images/ent-lepidoptera/images/2012_09_15/IMG_128681.JPG
(c) Museum of Comparative Zoology, Harvard University, some rights reserved (CC BY-NC-SA), https://mczbase.mcz.harvard.edu/specimen_images/ent-lepidoptera/images/2012_09_15/IMG_128682.JPG
(c) Museum of Comparative Zoology, Harvard University, some rights reserved (CC BY-NC-SA), https://mczbase.mcz.harvard.edu/specimen_images/ent-lepidoptera/images/2012_09_14/IMG_128602.JPG
Adapted by Allie Hay from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Papilio_troilus
Adapted by Allie Hay from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412843
Adapted by Allie Hay from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412845
(c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412844
(c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412849
(c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412846
(c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412847
(c) The Biomimicry Institute, some rights reserved (CC BY-NC), http://eol.org/data_objects/16885900
(c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31412855

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