Black Swallowtail butterflies are visiting my gardens earlier than in previous years. I’m thrilled by their presence and even happier to find my fennel plant loaded with caterpillars. Just as I feared though, a daily check on the fennel reveals a diminished amount of newly hatched caterpillars. They fall victim to predatory bugs and some birds. I found a great article on insects that eat Monarchs and other butterfly caterpillars. Butterfly Predators.
In years past I grew pots of dill with the purpose of saving caterpillars from predators. The idea worked and I was able to save quite a few and they reached maturity on my back porch. Unfortunately, this early in the season my dill sprouts are only a few inches tall. What do do?
A water-filled milk carton with a piece of screen rubber-banded around the top is a good solution. The screen is a must or I risk drowned caterpillars. Although the fennel was limp for a few hours after cutting, it soon perked up. I cut about three fronds, and might need to add more as the caterpillars eat. Because I didn’t want to hand-pick the caterpillars and risk harming them, I cut away just the small tip they were on and placed it within the larger fennel pieces. The caterpillars are doing well, this is day three of their protected feasting on the porch. As they grow I will add pots of twigs in the vicinity for them to begin their metamorphosis upon. In past years several caterpillars rejected the twigs and created their chrysalis on the porch screens and even the wall. This also worked great and all but one emerged unscathed by the human intervention.
Why do I do this? Butterfly populations are declining all over the world due to pollution, insecticides, carbon dioxide, loss of habitat, etc. Giving a few a helping hand might add hundreds more to the environment, and this makes the time I spend saving a few completely worthwhile. I left at least half of the caterpillars outside on the fennel. I’m hoping several will evade detection by hungry predators and make it to the chrysalis stage.