Caterpillar of the day: Papilio cresphontes

The Giant Swallowtail - Papilio cresphontes (Papilionidae)

Papilio cresphontes caterpillar resting on a lemon leaf. Photo: Wikipedia.org

The Ottawa Citizen reported today that the range of the Giant Swallowtail (Papilio cresphontes) butterfly has now reached Ottawa (click here to see the full article). Interestingly, I observed a butterfly earlier this May near Kilmarnock Lock that I had suspected was a P. cresphontes, but I thought that I must have been mistaken because - to my knowledge - the species didn't occur this far north.

A year ago macroecologist Jeremy Kerr, who studies range shifts in butterflies, had apparently predicted that P. cresphontes would reach Ottawa in three years. Kerr is a macroecologist, meaning that he studies large-scale ecological processes such as species range shifts of changes in species richness over large spacial scales. Butterflies are one of the main systems used in his research partly because reasonably accurate species richness and abundance data is concurrently available over both a long time scale and wide geographic range.

This beautiful butterfly has a wingspan approaching 15cm (range: 8.5-14cm). The fore wing (FW) length ranges from 55-62 mm with an average of 58.5 mm. Yes, this butterfly is quite large!

Papilio cresphontes adult. Photo: Wikipedia.org

Papilio cresphontes adult. Photo: Wikipedia.org

The caterpillar life stage starts out like other Papilio species, masquerading as a bird-dropping. Yet, unlike many Papilio caterpillars it does not change into a green caterpillar with eyespots (e.g. P. glaucus, P. troilus), or a caterpillar with repeating rings of different colours (e.g., Papilio polyxenes) in its later and larger instars. The caterpillar feeds on Rutaceae species, such as Citrus, Zanthoxylum americanum, Ptelea trifoliata, Ruta graveolens. Other Papilio species that similarly remain as bird droppings are all closely related and include: Papilio anchisiades, Papilio astyalus, Papilio erostratus, Papilio hectorides, Papilio thaos, and Papilio torquatus. The caterpillar gets to about 5.5 cm.

Papilio cresphontes caterpillar extending it's osmeterium. Photo: Wikipedia.org

If you see one of these butterflies, or any species for that matter, be sure to report you sighting at eButterfly.ca

**UPDATE: See a video about the recent northward migration of Papilio cresphontes here! **