Butterflies of
Australia
Plain Tiger
Danaus chrysippus
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
DANAINAE
Tribe - DANAINI
Danaus
chrysippus, male
Introduction
The
subfamily Danainae, which includes the Monarchs & Tigers, Nymphs and Crows,
comprises of about 190 species worldwide.
All
butterflies in this subfamily are thought to be toxic or distasteful to avian
predators. Their bodies contain toxins derived from the larval foodplants,
often supplemented by further toxins derived from pyrrolizidine alkaloids in adult food sources.
This form of defence is called Batesian mimicry. It is only effective because
the toxic species far outnumber the non-toxic species. If the situation was
reversed, and most of the butterflies attacked were palatable, the mimicry would
serve no purpose.
Monarchs and Tigers belong to the genus
Danaus.
They are large butterflies, characterised by their orange wings, which have a black
apex, and white subapical spots. On the males there is a patch of raised
androconial scales on the hindwings.
The
bright colours advertise their poisonous qualities
to birds in the same way that the bands of yellow and black of wasps
advertise the fact that they can sting. Any bird that attempts to eat the
butterfly will immediately vomit and suffer nausea and other side
effects. Birds have excellent memories and an ability to learn
from unpleasant experiences, so consequently avoid eating
similarly coloured butterflies in the future.
Danaus
chrysippus
is found across the
entire African continent and throughout tropical Asia. It also
occurs on most of the islands of the south Pacific.
In Australia it is
common in the north, becoming scarcer in the south, and with only occasional
records from Tasmania.
Danaus
chrysippus, male
Habitats
This species occurs in many habitats ranging from deserts to savannah
grasslands, dry deciduous woodlands, humid sub-tropical forests, gardens, parks
and cities at altitudes between sea level and about 1500m.
Lifecycle
The larval foodplants
include most genera of Periplocaceae and Asclepiadaceae. Some
species of these plants contain cardenolides ( heart depressants )
which are sequestered by the larvae and passed on to the adult
butterflies. Other species used by the larvae however do not
contain these cardenolides, consequently some adults are
inherently toxic, while others are harmless and edible. In fact
about 80% of adults are non-toxic at the time of emergence. During
their lifetimes however all adults obtain pyrrolizidine alkaloids
and other toxins which they sequester from various plants.
Danaus
chrysippus, male sequestering pyrrolizidine alkaloids
from a sage plant.
The caterpillars of chrysippus
are attacked by the host-specific parasitoid wasp
Apanteles chrysippi which accounts
for about 85% of larval mortality.
Adult behaviour
The butterflies are usually encountered in
three's and four's in the wet season, but can be found in greater
numbers during the dry season, when they often outnumber all other
species, especially in savannah / woodland and thorn scrub
habitats.
They have a slow undulating flight, with fairly shallow wing
beats. Both sexes patrol flowery areas, alighting periodically to
take nectar, or to imbibe fluid from ergot on the leaves and
stems.
In overcast weather,
or when roosting overnight, they hang suspended from twigs or
grass stems, in sheltered forest
edge habitats, sometimes in groups of half a dozen
or more individuals.
Danaus
chrysippus, male
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