Introduced purple loosestrife as host of native Saturniidae (Lepidoptera)

Purple loosestrife (Lythrum salicaria, Lythraceae) arrived in North America nearly 200 years ago. In 1969 we first found larvae of the native Cecropia (Hyalophora cecropia) and Polyphemus (Antheraea polyphemus) moths (Lepidoptera: Saturniidae) on loosestrife in the Hudson River Valley, New York, and we have since found Io (Automeris io) on this plant. A census of 4th and 5th instar saturniids in four 0.25 ha plots in purple loosestrife-gray dogwood (Cornus racemosa) wet meadows near Saugerties in 1984 indicated that Polyphemus and Cecropia larvae occurred much more frequently on loosestrife than on dogwood, a native host. The switch from native woody hosts to an introduced herb may have been facilitated by the dense shrub-like habit, high productivity, and high tannin content of loosestrife.