I haven’t seen many butterflies this summer, but they have obviously visited the backyard garden. Yesterday when I went out to collect some dill for pickle-making, I found these Black Swallowtail caterpillars munching my dill plants.
I watched while these two devoured stem after stem of the dill, eating their way from the ends of the delicate leaves down to the woody part of the stem. Every now and then, they stopped to eject a little square packet of excreta.
Black Swallowtail caterpillars exhibit a variety of color phases during development, as shown in these wonderful photos by Bob Moul.
Black Swallowtails prefer to lay their eggs on plants in the carrot family, especially dill, Queen Anne’s lace, fennel, parsley. This first generation of butterflies will mate and lay eggs, but then those larvae (second generation) will pupate over the winter, finally emerging when it becomes warm enough again the following summer to complete their metamorphosis and start the life cycle all over again. This means that the two generations of caterpillars have different programming for development, some completing their metamorphosis quickly within two weeks, but others entering a dormant phase that can last for months. Interesting control mechanisms at work here.