Butterflies of
Africa
Plain Tiger
Danaus chrysippus
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
DANAINAE
Tribe - DANAINI
Danaus
chrysippus, male, "form
chrysippus" ( "form alcippus"
has white hindwings )
Introduction
The
subfamily Danainae, which includes the Monarchs & Tigers, Nymphs and Crows,
comprises of about 190 species worldwide.
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 ( pheromone emitting ) scales on the hindwings.
All
butterflies in this subfamily are thought to be toxic or distasteful to avian
predators. Their bodies contain toxins which are derived from the larval foodplants,
and are often supplemented by further toxins derived from adult food sources.
The
bright colours of the butterflies 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 suffers the
unpleasant experience of tasting a
Danaus is unlikely to attack any similarly coloured
butterfly. This has led
many other
species to evolve adults which mimic chrysippus,
and thus avoid predation. These mimics include other toxic species such as
Acraea encedana, and also a smaller number of
palatable insects such as
Hypolimnas misippus.
Danaus
chrysippus
is found across the
entire African continent, throughout most of Asia south of the
Himalayas, on most of the islands of the south Pacific, and
across much of Australia.
In Africa the hindwings of
Danaus chrysippus are usually predominantly white,
a form known as alcippus. The illustrated
form chrysippus is very scarce in West Africa. In
East Africa however, it forms an element of between 10-50% of most populations.
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.
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 singly or in two's and
three's.
They have a slow undulating flight, with fairly shallow wing
beats.
Both sexes patrol flowery areas, alighting periodically to take nectar,
or to imbibe pyrrolizidine alkaloids from the leaves and stems.
In overcast weather,
and when roosting overnight, the butterflies hang suspended from
grass stems or dry twigs, often in clusters of up to half a dozen
individuals.
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