Page 269 - 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 Arizona
HABITAT Dry foothill or shrub-steppe gullies, streambeds, and hillsides
HOST PLANTS Thistle (Cirsium spp.)
NOTE Spiny, communal caterpillar that has many defenses
CONSERVATION STATUS Not evaluated, but common

ADULT WINGSPAN
1¾–2 in (45–50 mm)
CATERPILLAR LENGTH
1–1 ⁄ in (25–30 mm)
PHYCIODES PALLIDA
PALE CRESCENT 267

(W. H. EDWARDS, 1864)

Pale Crescent caterpillars hatch from an ordered mass of around
90 eggs, laid eight to nine days earlier on the underside of thistle
leaves at the plant’s mid-height. First-year thistles are preferred,
and mature, owering thistles are avoided. First and second

instars live communally in loosely woven silk nests, usually in a
fold of the host leaf. The survival strategy of this species includes
group behavior (synchronous reactions to disturbances), the
physical protection of its silken webs, concealment inside or
under leaves, avoidance (coiling up and dropping to the ground
when disturbed), and camou age.

The larvae usually develop to the fourth instar in about 18 days.
In most locations, the third or fourth instar enters dormancy
and overwinters, resuming feeding and development in the
following spring. Adults y from the middle of May to July.

Males perch conspicuously and chase females, which spend
much of their time low in the vegetation, avoiding males.

The Pale Crescent caterpillar is dark brown
to black with numerous white spots and several
broken, longitudinal, white stripes. In some
populations, the white markings coalesce, making
the caterpillar largely white. The spines are black
and clumped, and have pronounced orange
bases. The head is shiny black, sometimes with
orange patches dorsally. Actual size