Butterflies of Mexico, USA & Canada
Spicebush Swallowtail
Pterourus troilus  LINNAEUS, 1758
subfamily - PAPILIONINAE
Pterourus troilus, USA  Adrian Hoskins
Back in the 18th century when Linnaeus created the System Naturae, the word Papilio was used as the genus name for every known species of butterfly in the world. Since then much has been learnt about the relationships between different species. Consequently most have been reassigned to new genera, and only about 215 of the 17600 currently known species are retained in Papilio.
There are 30 Papilio species in the Australian region, 60 in the Oriental region, 40 in the Holarctic region and 54 in Africa. The taxonomy of North and South American 'Papilio' species has recently been revised, with the effect that almost all South American species and several North American species have been transferred to Heraclides, or in the case of troilus, to Pterourus.
This species is regarded as a Batesian mimic of the noxious Battus philenor.

Pterourus troilus is restricted to the eastern states of the USA and south-east Canada.

Pterourus troilus, USA  Adrian Hoskins

This species is found in open deciduous woodland, at altitudes between 0-1500m.
The egg is greenish-white and is laid singly on the under surface of a leaf of Sassafras, Lindera, Cinnamomum, Persea ( Lauraceae ) or less commonly Liriodendron or Magnolia ( Magnoliaceae ).
The larva lives solitarily within a shelter constructed by rolling a leaf to form a flap or tube, which is fastened together with strands of silk. Prior to the final instar the upper part of the body is yellowish green. There is a broad yellow lateral stripe, below which the body is pale orange. In the final instar the body is orange above and below the stripe. The abdominal segments have two sub-dorsal rows and one lateral row of blue spots. On the thoracic segments there are two pairs of conspicuous pale orange ocelli, the frontal pair having black centres. If the larva is molested it hunches up, causing the ocelli to expand. This gives the larva a threatening appearance which undoubtedly deters small predators. If molested further, the larva produces from behind its head an eversible fleshy orange forked structure called an osmaterium which emits pungent deterrent chemicals. Experiments with captive birds have shown that the chemicals are ineffective against them, but that they are capable of deterring ants, and parasitic wasps and flies.
The pupa is light brown mottled with paler markings. It is attached by the cremaster and a silken girdle to a woody stem or tree trunk.
Adult behaviour

Males sometimes imbibe mineralised moisture from damp ground. Both sexes visit a wide range of herbaceous and bushy plants for nectar.


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