Caterpillars on walkabout

This time of year, many caterpillars are leaving their host plants and going on "walkabout", searching for the perfect place to pupate and spend the winter, before emerging as adults in the spring. While there are also many species that overwinter as eggs and adults, you may notice more caterpillars this time of year because of this habit of searching out a hiding spot.  Woolly bear caterpillars overwinter as larvae, before spinning a cocoon in late winter/early spring, and emerging as the Isabella tiger moth.  Polyphemus moths have a large green caterpillar about as big as your finger, and are sometimes seen crossing sidewalks looking for a good place to spin a cocoon.  They feed on oak and maple, sometimes other trees, and turn into very large, buckskin-colored adults with black and blue eyespots.  Swallowtails, such as anise and western, have solid green, brown, or green and black striped caterpillars, depending on the species.  They form an upright chrysalis attached to twigs, and I've also found several of them attached to the underside of a piece of plywood leaning against our house.
If you find any that you would like to rear, place them in a container in a cool (but that doesn't freeze in the winter), dark place, such as an outdoor storage closet or enclosed porch.  Check on them periodically through the winter in the event they become too warm and emerge early.  Start checking them daily in March or April, and move the pupae to a larger container with rough walls or a stick they climb on once they emerge.

Anise swallowtail larva (Papilio zelicaon)

Anise swallowtail chrysalis