Family Papilionidae

Parnassians and Swallowtails

The Papilionidae are the smallest family of butterflies. However, because of their large size and great beauty they are probably the best known butterflies to specialists and naturalists alike. The family contains about 570 species worldwide, with about 40 species found in North America and 18 in Canada. Many have tails on the hindwing, which gives them their common name. All have six fully functional legs in the adult stage. Their larvae feed on dicotyledonous plants. In some tribes they feed on poisonous plants; these larvae store the poisonous chemicals until the adult stage, which advertises this distastefulness with vivid colour patterns. The larvae generally lack spines, but have an osmeterium, a strong-smelling forked organ that can be protruded from the thorax to repel predators.

Subfamily Parnassiinae

Parnassians

There are about 50 species of parnassians in the northern hemisphere, with five in North America, four of which are found in Canada. The fifth species is Parnassius behrii W.H. Edwards, which occurs at high altitudes in California (Shepard et al., 1994).

These are butterflies of the mountains. Some fly at very high altitudes and can occasionally be seen flying over snow. Butterflies that live at high altitudes tend to live in colonies that are isolated from one another, even in mountain ranges that are close together. As a result, many genetically isolated populations develop localized forms and subspecies. This is certainly true of the parnassians.

Although they look quite different from the true swallowtails, the parnassians are closely related. They share the osmeterium, a retractable organ that has a musky predator-repelling smell. The larvae can squeeze into small places and use this ability to enable them to pupate underground or under rocks. They are supposedly mimics of poisonous millipedes.

These butterflies are adapted to cold, windy climates. Their hairy bodies help them retain heat. At high altitudes, they tend to be darker in coloration, which allows them to absorb more solar radiation. They fly close to the ground or rest down in the grass to prevent heat loss from the wind. The adults often rest with wings flat on rocky surfaces to absorb heat from the sun.

Parnassians do not have a courtship behaviour as do most butterflies. Instead, the males simply patrol waiting for females. When one is sighted, they approach directly and immediately mate. They are unique in having a sphragis, a waxy pouch that the male glues onto the female after mating to prevent her from mating with other males.

Subfamily Papilioninae

Swallowtails

This subfamily occurs on all continents and contains all of the other swallowtail species except one, the primitive Baronia brevicornis (Salvin) of southern Mexico. They are large, mostly tropical butterflies and probably the best-known butterflies to the general public. In addition to their size, they often visit gardens and avidly sip nectar from flowers. All of the 14 Canadian species have conspicuous tails on the hind wings.

The larvae also have distinctive traits that help to identify them. When disturbed, the larva extends its osmeterium, a special organ on the body just behind its head that looks like a fleshy pair of feelers. This gives off a strong disagreeable odour that deters would-be predators. The young larvae often resemble bird droppings; their mottled white and black coloration is believed to confuse birds and lizards that might attack them. The pupae have a distinctive silken girdle that holds them to the plant upon which they have pupated.

In the tropics, many swallowtail larvae feed on plants, such as Aristolochia, that contain strong toxins to deter herbivores, including butterfly larvae. These swallowtail larvae, including those of one species that reaches Canada, the Pipevine Swallowtail, have evolved the ability to take advantage of this situation and store the toxins in their bodies, which make them distasteful or even poisonous to their predators.

The males of some species of swallowtails seek out a hilltop and establish a territory to patrol. The males often emerge first from the pupa. The emerging females then seek out hilltops to mate with the waiting males.

Of the 14 swallowtail species found in Canada, two, the Zebra and the Pipevine Swallowtails, belong to genera that only reach southern Ontario. Ten of the remaining species fall into two groups, the Papilio glaucus and Papilio machaon groups, that have caused confusion and disagreement among lepidopterists in identification and classification. Over the years, the definitions of species and subspecies have shifted dramatically. Physiological and genetic studies by a large number of authors, e.g., Brower (1959), Fisher (1977), Sperling (1987), Hagen et al. (1991), and Tyler et al. (1994), have greatly improved our understanding of these groups and the arrangements in this book largely follow these determinations. Species identifications, especially in the difficult Papilio machaon group, can best be made by referring to the subspeciesaccounts and the distribution maps in the species descriptions.

© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.