Papilio Troilus - Habitat

Habitat

The host plants of the Spicebush Swallowtail are most commonly either spicebush (Lindera benzoin) or sassafras (Sassafras albidum). Other possible host plants include Sweet bay (Magnolia glauca) and Prickly Ash (Zanthoxylum), as well as tulip tree (Liriodendron tulipfera), sweetbay (Magnolia virginiana), camphor (Cinnamomum camphora) and redbay (Persea borbonia). Redbay and Swampbay are the primary host plants for members of the Papilio troilus ilioneus strain, while spicebush and sassafras as the primary hosts for Papilio troilus troilus. However, when given the choice between spicebush and sassafras, the P. troilus troilus showed no significant preference for either.

Additionally, P. troilus ilioneus live only on redbay because that is the primary host plant within the Southern range. However, in a test of P. troilus troilus and P. troilus ilioneus on redbay, sassafras and spicebush, although the P. troilus ilioneus had higher growth and survival rates on redbay than the P. troilus 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. This fact is especially noteworthy because Lauraceae are distantly related to the host plants of other species that are food for Papilio caterpillars. 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 2-4 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. troilus ilioneus strain, found in Florida, mostly feeds on redbay, while P. troilus 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 ilioneus strain was typically larger in size than the 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 camphortree, 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 butterly, 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.