Page 41 - The Book of Caterpillars: A Life-Size Guide to Six Hundred Species From Around the World

BUTTERFLY CATERPILLARS

FAMILY Papilionidae
DISTRIBUTION United States, south to Central America
HABITAT Forests and meadows
HOST PLANTS Pipevine (Aristolochia spp.)
NOTE Unpalatable caterpillar whose color can vary according
to temperature
CONSERVATION STATUS Not evaluated, but common

ADULT WINGSPAN
2¾–5 in (70–130 mm)
CATERPILLAR LENGTH
2–2¾ in (50–70 mm)
BATTUS PHILENOR
PIPEVINE SWALLOWTAIL 39

(LINNAEUS, 1771)

Females of the Pipevine Swallowtail lay clusters of up to 20 eggs,
so the young caterpillars feed in groups. This enables them to
resist plant defenses, such as hairs on the plant’s surface called
trichomes. Older caterpillars are solitary and eat leaves, stems,
and seeds. The larvae can consume up to half of their host plant’s

foliage, and significantly increase plant mortality and reduce
seed production. The aristolochic acid found in host plant
foliage is converted by the caterpillars into chemical defenses
and passed by them to pupae, adult butterflies, and eggs. Hence

all stages are unpalatable to predators, and even parasitoids are
deterred from attacking them.

The caterpillars can be polymorphic. Red caterpillars have
been found to occur at temperatures greater than 86°F (30°C),
and in Texas their numbers increased with rising daily
temperatures. The larvae thermoregulate by climbing on to non-
host vegetation to avoid excessive heat. Very similar caterpillars
are found in very different-looking, but related, “birdwing”

butterflies from the Old World, which also feed on pipevines.
Actual size

The Pipevine Swallowtail caterpillar has eshy
lament projections on each segment—the
longest on the thoracic segments, especially the
rst. Dorsally, there are paired orange-red spots.
The larvae are either black or smoky red; black
is the norm, but the red phenotype occurs in
western Texas and Arizona, where temperatures
are highest. Larvae in Florida have longer
projections than those in California; the two
populations are considered di erent subspecies.