Performance of eastern black swallowtail (Papilio polyxenes) larvae on native and introduced host plants

The introduced hosts of the eastern black swallowtail (Papilio polyxenes) are of wide distribution and high abundance throughout central Illinois, whereas its native hosts are typically patchily distributed and only locally abundant. A study was conducted to compare the ability of P. polyxenes larvae to feed and develop on its native and introduced hosts. The performance of larvae on each of nine local host plants, of which six are native and three are introduced, was measured in two different experiments. In the first experiment, food utilization indices of fifth instar P. polyxenes larvae on each host plant were measured. In the second experiment, larvae were reared on each host. The survival rates and development times of first instars were recorded. The survival rates and development times of first instar larvae reared on introduced host plants were found to be different from those reared on native host plants. Studies such as this one can demonstrate how human activity, including the accidental introduction of invasive weeds, can alter not only the abundance and distribution of a native species but also its physiology and behavior.