Editing Papilio rutulus (section)

==Biology==
Butterflies emerge from winter chrysalids between the spring months of February and May, the date depending on the temperature, so they are seen earlier in the more southerly and more coastal parts of their range. They are very active butterflies, rarely seen at rest. The adult females lay up to a hundred eggs in total. The eggs are deep green, shiny, and spherical. They are laid singly, on the undersides of leaves.

The [[caterpillar]]s emerge about four days later. They can feed on the leaves of a variety of trees, and the predominant food plant varies across their range; trees commonly used include [[Populus sect. Aegiros|cottonwood]], [[willow]], [[quaking aspen]], and many others.

The caterpillars molt four times, eventually reaching a length up to 5&nbsp;cm before pupating. In summer, the butterfly can emerge as quickly as 15 days after the caterpillar pupates, but when the caterpillar pupates in the fall, the butterfly does not emerge until the spring.

The males often congregate, along with other species of swallowtail, at pools and along streams and rivers; they [[mud-puddling|drink from the water and mud]], extracting minerals, as well as moisture. Females lay eggs singly on the surface of host plant leaves. Caterpillars feed on leaves and rest on silken mats in shelters of curled leaves. Chrysalids [[Hibernation|hibernate]].