There is a love it or hate it attitude with this butterfly
among gardeners. Most folks love the butterfly, but herb gardeners hate the
caterpillar. The Black Swallowtail caterpillar feeds on plants that are members
of the Apiaceae or Carrot Family
which includes parsley, dill, fennel, celery, cilantro, anise, caraway and
Queen Ann’s lace. The hungry caterpillars can devour a patch of parsley in no
time.
The Black Swallowtail will over winter in our area as a pupa
and is one of the first butterflies to show up in the spring. These are large
butterflies that are mostly black with a double row of yellow spots along the
wing margins. The underside of the lower wing has orange spots. If you look
closely you can tell a male from a female. The yellow spots on the male are
larger and sometimes run together to look like a band of yellow. Both males and females have an iridescent
blue patch on the lower wing but on the female the patch is larger. So if it has small yellow spots and a big
blue patch it is a female. If it has big yellow spots and a small blue patch it
is a male. Both will also have an orange eye spot with a black center on the
lower wing near the tail. Eye spots on butterflies and moths are common and are
believed to confuse or scare predators.
Butterflies are cold blooded and rely on the sun warm them
up so they can fly and feed. You may have noticed butterflies are rarely seen
on cloudy days. In the morning they sit in a sunny place and warm up so they
can fly. By the way, the best time to photograph butterflies is in the morning
while they are sunning.
The black color allows the Black Swallowtail to warm up
quickly. Black is a popular color for many of our local butterflies. The
Palamedes Swallowtail, the Giant Swallowtail and the Morning Cloak are all predominately
black.
The caterpillar of the Black Swallowtail starts out mostly
black but when it gets big enough for you to see, it will be green with black
stripes. Look closer and you will see yellow spots down the sides of the
caterpillar. Of course, this caterpillar will be easy to identify because it is
eating your favorite herbs.
If you want to have some fun, take along skinny stick and
gently poke the caterpillar. If it feels threatened, a horn like gland called
an osmeteria will pop out of
its head and release a chemical with a stinky odor. Do not try this with your finger or you will
be washing your hands for days trying to wash the stink off.
Ever wonder what they ate before Europeans brought culinary
herbs for the caterpillars to dine on? There are some native “weeds” in the Apiaceae
family which can be found in our gardens and along waysides. Roughfruit
scaleseed or Spermolepis divaricate is
a small dill-like plant (24”) with a very small umbrel of tiny light
green flowers. It was first described in 1788 by local botanist Thomas Walter. When I first saw this plant in my garden, I
thought my dill had re-seeded itself. The foliage has a carrot like scent.
Roughfruit scaleseed is a common name that is more than a mouthful. I find it
hard to remember, I think I will rename this plant Carolina Dill Weed.
Mock Bishopweed or Ptilimnium
capillaceum looks like a shorter dill plant (12”) with white flowers that
are showier than Carolina Dill Weed. Mock Bishopweed is often found in wet and
brackish coastal areas. French botanist Andre Michaux first described this
plant in our area in 1803. When these
weeds pop up in my garden, I usually leave them alone and let the Black
Swallowtail butterfly lay their eggs on them instead of my parsley. Maybe it will work someday.
