Papilio troilus, the spicebush swallowtail or green-clouded butterfly, is a common black swallowtail butterfly found in North America."Simply Butterflies," Accessed March 17, 2011, http://www.simplybutterflies.com/Backyard_Butterflies.html It has two subspecies, Papilio troilus troilus and Papilio troilus ilioneus, the latter found mainly in the Florida peninsula.Hall, Donald; Butler, Jerry (Aug 2007). "Spicebush Swallowtail," Institute of Food and Agricultural Sciences, University of Florida. http://www.edis.ifas.ufl.edu/pdffiles/IN/IN110700.pdf The spicebush swallowtail derives its name from its most common host plant, the spicebush, members of the genus Lindera.
The family to which spicebush swallowtails belong, Papilionidae, or swallowtails, include the largest butterflies in the world. The swallowtails are unique in that even while feeding, they continue to flutter their wings. Unlike other swallowtail butterflies, spicebushes fly low to the ground instead of at great heights.Scott, James. Butterflies of North America. Stanford: Stanford UP, 1986.
Distribution and habitat The spicebush swallowtail is found only in the eastern US and southern Ontario, but occasionally strays as far as the American plains states, Cuba, Manitoba and Colorado. While still larvae, spicebush swallowtails remain on the leaf of the plant on which they were laid. As adults, the butterflies do not limit their flight geographically and instead are motivated mostly by availability of water and nectar and mates within the species' range.Mickley, J. and A. Fraser (2006). "Papilio troilus" (On-line), Animal Diversity Web. Accessed March 30, 2011, http://animaldiversity.ummz.umich.edu/site/accounts/information/Papilio_troilus.html
This primarily black swallowtail is normally found in deciduous woods or woody swamps, where they can be found flying low and fast through shaded areas. Females tend to stay in open plains,Scriber, J., Y. Tsubaki and R. Lederhouse. Swallowtail butterflies: their ecology and evolutionary biology. Scientific Publishers: Gainesville, Fla. 1995. while males are typically found in swamp areas.
Papilio troilus troilus The more widespread subspecies of spicebush swallowtail is prevalent throughout the Eastern United States, from New England to Wisconsin, west to Illinois, Wisconsin, North Dakota and Nebraska. It also abounds in Texas and Colorado.Hamilton, Tyler A. The Swallowtail Butterflies of North America. Naturegraph: Heraldsburg, Calif., 1975. Temperature may be a limiting factor for the spread of P. t. troilus, as in experimental conditions, they do not fare well at or above nor are they capable of flourishing at or below .Scriber, J. Mark, Keegan Keefover and S. Nelson, (2002). "Hot summer temperatures may stop movement of Papilio Canadensis butterflies and genetic introgression south of the hybrid zone in the North American Great Lakes Region." Ecography 25: 184-192.
Papilio troilus ilioneus The smaller subspecies of P. troilus is confined to the Southeastern coastal United States, namely throughout Florida and along coastal Georgia and in places in Texas.
Description
P. t. troilus Typically, the wingspan of a spicebush swallowtail ranges from . Adults are primarily black/brown in color, with a trademark green-blue (male) or bright blue (female) splotch in the shape of a half moon on the hindwings. The forewing has a border of cream-colored, oval spots. In the middle portion of the wing, the spots can be moon shaped and a light blue in color. Both sexes have cream-yellow moon-shaped spots on the edges of the hindwings and a bright orange color spot at the base of the wings.Minno, Marc C.; Minno, Maria. Florida Butterfly Gardening: A Complete Guide to Attracting, Identifying, and Enjoying Butterflies of the Lower South. Gainesville: UP of Florida, 1999. In females, the orange spot at the base of the wings will turn a greenish-white shade in summer, but not the spring.
On the underside of the hindwing, there will be a dual row of orange spots, which distinguishes it from the pipevine swallowtail, which only has a single row of spots. In between these rows, there is more blue or green coloring. Characteristically, the median (inner) orange spots are discontinuous, allowing the blue or green coloring to spread medially.
P. t. ilioneus The distinguishing difference in color between the two subspecies is evident where the spots, which are blue in color on the hindwing of the P. t. troilus, are more yellow in color in P. t. ilioneus. Additionally, splashes of blue can trail all the way down the tail of P. t. ilioneus.
Ecology The host plants of the spicebush swallowtail are most commonly either spicebush (Lindera benzoin) or white sassafras (Sassafras albidum).Klots, Alexander. A Field Guide to Butterflies. Boston: Houghton Mifflin, 1964. Other possible host plants include prickly ash (Zanthoxylum),Attributes of Papilio Troilus, Accessed March 17, 2011, https://www.butterfliesandmoths.org/species/Papilio-troilus as well as tulip tree (Liriodendron tulipifera), sweetbay (Magnolia virginiana), camphor (Cinnamomum camphora) and redbay (Persea borbonia). Redbay and swampbay (Persea palustris) are the primary host plants for members of the P. t. ilioneus strain, while spicebush and sassafras as the primary hosts for P. t. troilus.Nitao, James; Ayres, Matthew; Lederhouse, Robert; Scriber, Mark J. (Aug 1991). "Larval Adaptation to Lauraceous Hosts: Geographic Divergence in the Spicebush Swallowtail Butterfly," Ecology 72 (4): 1428-1435. However, when given the choice between spicebush and sassafras, the P. t. troilus showed no significant preference for either.Carter, Maureen; Feeny, Paul; Haribal, Meena (1999). "An Oviposition Stimulant for Spicebush Swallowtail Butterfly, Papilio Troilus, From Leaves of Sassafras albidum." Journal of Chemical Ecology 25 (6).
Additionally, P. t. ilioneus live only on redbay because that is the primary host plant within the Southern range. However, in a test of P. t. troilus and P. t. ilioneus on redbay, sassafras and spicebush, although the P. t. ilioneus had higher growth and survival rates on redbay than the P. t. troilus, as a holistic group, both subspecies performed better on sassafras or spicebush over time.
In general, spicebush swallowtails tend to stick to plants that are members of the family Lauraceae. The preference for Lauraceae is so consistent among spicebush swallowtails that under experimental conditions, when placed in an environment with leaves other than Lauraceae, P. troilus died without eating anything.Scriber, J. Mark, Michelle Larsen, Geoff Allen, Paul Walker and Myron Zalucki, (2008). "Interactions between Papilionidae and ancient Australian angiosperms: evolutionary specialization or ecological monophagy?" Entomologia Experimentalis et Applicata 128: 230-239. This fact is especially noteworthy because Lauraceae are distantly related to the host plants of other species that are food for Papilio caterpillars."Swallowtail Butterflies," Accessed March 17, 2011, https://www.uky.edu/Ag/CritterFiles/casefile/insects/butterflies/swallowtail/swallowtail.htm The fact that spicebush swallowtails live and feed primarily on Lauraceae only is noteworthy also because most other varieties of swallowtail butterflies are nowhere near as specific. Part of the reason for the selective nature of P. troilus and host plants may have to do with the requirement of positive stimuli to confirm that a plant is Lauraceae among P. troilus before they will feed on it, while P. glaucus, for example, will at once try to feed on any plant presented to it.
The insistence on feeding primarily on Lauraceae has its advantages for spicebush swallowtails. They are able to feed two to four times more adeptly and efficiently on Lauraceae than P. glaucus on the same plant, for example, who feed on Lauraceae as well as other types of plants. In addition, there has not been any other Lepidoptera species which feeds as efficiently as the P. troilus on spicebush. However, none of the host plants of Papilio troilus occur throughout the full range of the spicebush swallowtail. As stated above, the P. t. ilioneus strain, found in Florida, mostly feeds on redbay, while P. t. troilus feeds on either sassafras or spicebush. In a study, it was found that those spicebush swallowtails that normally feed on redbay did not grow as well on spicebush or sassafras during the first instar of development, while all insects studied grew better throughout the larval period on sassafras or spicebush. In addition, the P. t. ilioneus strain was typically larger in size than the P. t. troilus.
In a recent study, 3-trans-caffeoyl-muco-quinic acid was found to be the substance that compelled spicebush swallowtails to lay their eggs on members of Lauraceae. However, 3-trans-caffeoyl-muco-quinic acid is a component of the extract from sassafras plants but not from spicebush, redbay or camphor tree, the other top three host plants of spicebush swallowtails. This substance is not necessarily itself the stimulant but instead activates another as yet unknown compound that thus compels the spicebush swallowtail to lay eggs. Thus, this substance may hold the link for why some spicebush swallowtails prefer to lay eggs on sassafras rather than spicebush. In addition, 3-trans-caffeoyl-muco-quinic acid is a member of a family of acids, hydroxycinnamic acids, which are present in oviposition stimulants for some members of all five families of swallowtail butterflies. Hydroxycinnamic acids are also present in the extracts from host plants for two other species within the genus Papilio: the black swallowtail butterfly, P. polyxenes, and P. protenor. Thus, hydroxycinnamic acids may help explain why many types of swallowtails choose to oviposit on the plants that they choose.
Food sources Spicebush swallowtails gain sustenance from eight major sources. Joe-Pye weed, jewelweed, and honeysuckle are favorite sources of nectar for the adults. They have also been known to drink nectar from lantanas, as well as thistles, milkweeds, azalea, dogbane, mimosa, and sweet pepperbush.
Life cycle
When female swallowtails decide which leaf to oviposit on, they frequently will drum their forelegs toward a leaf to identify it. Their forelegs have chemoreceptors located in the foretarsi that assess the chemical makeup of the leaf and use that information to decide if it is an acceptable spot. In general, females have shorter and denser sensilla on their forelegs than males, which may be a result of their having to sustain frequent heavy strokes.
The eggs of the spicebush swallowtail are greenish white in color, are fairly large and are laid one or two at a time on a spicebush leaf. Once hatched, the young larvae chew through the leaf from the edge to the midrib, about from the tip of the leaf. The larva lies on the midrib and exudes silk. Upon drying, the silk contracts and causes the leaf to fold up around the larva to form a shelter. At first, young larvae are brownish.Field Notes from the Beiser Field Station: October 7, 2008, The Spicebush Swallowtail, Accessed March 14, 2011, https://www.marietta.edu/~biol/biomes/spicebush.htm. The brown color of the larvae is independent of leaf color and will occur even on a green leaf.Shapiro, A.M., (1976). "Seasonal polyphenism." Evolutionary Biology 9: 229-253. A folded leaf serves as the home for the young larvae. During the day, the larvae remain in the shelter so as to avoid predators and come out at night to feed. Additionally, if larvae are disturbed while rolled up in the leaf, they emit a foul-smelling substance.