Mexico, USA & Canada
Family - PAPILIONIDAE
Pterourus glaucus, Indiana, USA ©
Back in the 18th
century when Linnaeus created the System Naturae, the word
Papilio was used as the genus name for
every known species of butterfly in the world. Since then much has
been learnt about the relationships between different species.
Consequently most have been reassigned to new genera, and only about
215 of the 17600 currently known species are retained in
There are 30
Papilio species in the Australian
region, 60 in the Oriental region, 40 in the Holarctic region and 54
in Africa. The taxonomy of North and South American 'Papilio'
species has recently been revised, with the effect that almost all
South American species and several North American species have been
transferred to Heraclides, or in the
case of glaucus to
Pterourus glaucus is one of several
species that share the tiger pattern of black stripes on a cream
background. Only the males have the tiger pattern - females are
plain chocolate brown on both wing surfaces. They have a series of
submarginal cream coloured crescents on both wings, and on the
hindwings also have a series of post-median blue crescents, and red
anal and apical spots.
Four of the
remaining "tiger" swallowtails - canadensis,
alexiares and rutulus were once
considered to be subspecies of glaucus,
but are now recognised as true species.
P. glaucus is restricted to the central
and eastern states of the USA.
This species is
found in open deciduous woodland, at altitudes between sea level and
The eggs are
greenish-yellow, speckled with brown. They are laid singly on leaves
of the foodplants which include Prunus,
( Rosaceae ), Populus ( Salicaceae ),
Acer ( Aceracaea ),
Tilia ( Tiliaceae ), Carpinus,
Alnus ( Betulaceae ),
Liriodendron ( Magnoliaceae ) and
various other trees and shrubs.
when small are dark brown above, greyish below, and are marked with
a white dorsal saddle. When at rest on the upperside of leaves they
greatly resemble a bird dropping.
When fully grown
the caterpillars are plump, mid-green in colour, and have a series
of small blue dorsal and mid-dorsal spots. On the 3rd thoracic
segment there is a pair of yellowish ocelli, each with a black
"iris" and a central white "reflection" mark. If the caterpillar is
molested it hunches up, causing the ocelli to expand and take on a
threatening appearance which probably has the effect of deterring
avian and mammalian predators. If molested further, the larva
produces from behind it's head an eversible fleshy orange forked
structure called an osmaterium, which
emits pungent chemicals.
Experiments with captive birds have demonstrated that the chemicals
are ineffective against them, but they are capable of deterring
ants, and predatory / parasitic wasps and flies.
The chrysalis is
light brown, mottled with olive or black, with a brown lateral
stripe and a pale dorsal stripe. It is attached by the cremaster and
a silken girdle to a woody stem, tree trunk, or to broken twigs or
dead leaves on the ground. The pupae hibernate overwinter.
Males patrol back
and forth along roadsides and woodland rides in search of females,
and in hot weather aggregate in groups of up to 20 to imbibe
mineralised moisture from damp ground. They also feed at carrion and
dung. Both sexes nectar at Lantana and
many other wild flowers.
Pterourus glaucus, Tennessee, USA ©