Giant Swallowtails are at the northern edge of there range here in central Wisconsin.Â Some years we have only a few, and some years there are hundreds.Â There’s some debate about whether the butterflies overwinter here, or fly up from the south in the spring.Â The earliest I’ve seen one here – Buffalo County, WI – was May 29 (in 2006).
The caterpillars of the Giant Swallowtail eat plants in the citrus family (Rutaceae).Â Here in Wisconsin, their only food is Prickly Ash (Zanthoxylum americanum).
Egg on Prickly Ash leaf – on top of leaf.Â All the eggs I’ve seen were laid on the top side of leaves.
Early instar caterpillar.Â Caterpillars also seem to prefer the tops of leaves, or the top side of the leaf stalk.
Later instar caterpillar
Caterpillar with osmeterium extended
Puddling on the driveway
Comparison of Tiger and Giant Swallowtails
Buffalo County, Wisconsin