Page 262 - The Book of Caterpillars: A Life-Size Guide to Six Hundred Species From Around the World

BUTTERFLY CATERPILLARS

FAMILY Nymphalidae
DISTRIBUTION Western North America, from British Columbia to
southern California
HABITAT Mountain slopes, canyons, watercourses, parks, and gardens
HOST PLANTS Mountain Balm (Ceanothus velutinus), Deerbrush (Ceanothus
integerrimus), and Redstem Ceanothus (Ceanothus sanguineus)
NOTE Spiny, gregarious caterpillars that reportedly produce
“millions of shimmering pupae”
CONSERVATION STATUS Not evaluated, but common

ADULT WINGSPAN
2⅜–2 ⁄ in (60–65 mm)
CATERPILLAR LENGTH
1¾–2 in (45–50 mm) NYMPHALIS CALIFORNICA
CALIFORNIA
TORTOISESHELL
260
(BOISDUVAL, 1852)

California Tortoiseshell caterpillars hatch from eggs laid in

clusters of up to 250 four to ve days earlier on the upper and

lower surfaces of host plant leaves. The rst instars partially
consume the eggshell, then feed on the host plant. Early instars
feed only on new growth and also use silk to cover and join
leaves together. The caterpillars feed and rest openly and are
gregarious in the rst three instars, dispersing in the fourth and

fth instars. Adults emerge about ve weeks after eggs are laid.

When disturbed, larvae of the rst three instars jerk their heads

in unison to intimidate predators. The heavily sclerotized
posterior segments in third and fourth instars resemble the head
capsule, giving the caterpillar a two-headed appearance, which
may divert the attention of birds. Reports of acres of defoliated
Mountain Balm and “millions of shimmering pupae” suggest
that caterpillar survival can be excellent. The species is subject
to periodic population explosions, and adults are long lived as
well as migratory.

The California Tortoiseshell caterpillar is black
with profuse long, white setae on the body and
head. Spines are either orange or black with
bulbous, orange or black bases. A pair of
interrupted, dorsal, white or yellow lines may
be present. The posterior two segments are
Actual size heavily sclerotized.