[4] 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.

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.

Females tend to stay in open plains,[6] while males are typically found in swamp areas.

[7] 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 36 °C (97 °F) nor are they capable of flourishing at or below 14 °C (57 °F).

[9][failed verification] 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.

[7] Characteristically, the median (inner) orange spots are discontinuous, allowing the blue or green coloring to spread medially.

[12] Other possible host plants include prickly ash (Zanthoxylum),[13] as well as tulip tree (Liriodendron tulipifera), sweetbay (Magnolia virginiana), camphor (Cinnamomum camphora) and redbay (Persea borbonia).

[16] This fact is especially noteworthy because Lauraceae are distantly related to the host plants of other species that are food for Papilio caterpillars.

[14] 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.

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.

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.

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.

[21] Once they have reached the adult stage, Papilio troilus can live anywhere from two days to two weeks dependent on resource availability and predator avoidance.

[5] Spicebush swallowtails (along with P. palamedes) are able to thermoregulate their thoraxes better than other Papilio species, perhaps due to their darker body and wing color.

[6] Spicebush swallowtails often engage in puddling, a type of behavior which occurs while adults are flying in search of food or mates.

Puddling reflects the fact that while engaging in either feeding or mating behavior, i.e. when they are away from home, spicebush swallowtails tend to stay in groups.

Males are less concerned with direct sunlight during mating because their thoracic temperature rises while performing vigorous courtship dances.

Males may perform these courtship dances both to females perched on host plants as well as those flying freely.

While the larvae are in the early stages, they are dark brown and thus appear to resemble bird droppings, which encourages predators to leave them alone.

[3] When the larvae have progressed to their fourth and last instar and are nearly ready to pupate, they turn a yellow-green color and are marked by two large black dots with a white highlight.

The placement of these dots on the swollen thorax creates the illusion that the caterpillars are common green snakes.

[20] For many spicebush swallowtails, the osmeterium is red, thus creating the illusion of a snake tongue and even further enhancing the disguise.

[2] There are other adult butterflies which mimic the poisonous B. philenor, including P. polyxenes, P. glaucus, C. promethea and L. astyanax, but P. troilus most closely resembles it.

An attack from a predator focused on the "false head" will leave the butterfly itself unharmed, though with slightly damaged wings.