Western Tiger Swallowtail
Description 2 3/4 - 3 7/8" Above and
below, lemon-yellow with black tiger-stripes
across wings and black yellow-spotted
margins. 1 or 2 orange spots and several
blue spots near black tail on HW; blue
continuous all around outer margin of HW
Yellow spots along outer black margin of FW
below run together into band; uppermost spot
on border of HW above and below is yellow.
Life Cycle Egg deep green, shiny,
spherical. Caterpillar, to 2", deep to light
green, swollen in front, accentuating large
yellow eyespots with black and blue pupils.
Dark brown, woodlike chrysalis overwinters
slung from a twig or tree trunk. Hosts more
limited than those of eastern Tiger, include
willows, poplars, and aspens several alders
Flight February in S. California, May in
Washington, normally June-July in mountain
areas. Up to 3 broods in low altitudes and
latitudes, 1 in cooler places with shorter
seasons. Present most of summer.
Habitat Widespread, but normally near
moisture - canyons, watersides, trails,
roadsides, parks and gardens; sagelands
and mesas with creeks.
Range British Columbia south to Baja
California, east through Rockies to Black
Hills, and High Plains of Colorado and New
Mexico. Rare east of Rockies.
Discussion The Western Tiger may be
the most conspicuous butterfly in the West.
The eastern and western species essentially
replace each other along a diagonal line,
northwest to southeast, although there may
be some slight hybridizing along the dividing
Such east-west species-pairs are not
unusual among butterflies. In Western
canyons, males of several species of
swallowtails gather in spectacular numbers
around mud puddles or beside streams, with
the Western Tiger usually predominating.