Butterflies of
Africa
Encedon Acraea
Acraea encedon
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
HELICONIINAE
Tribe - ACRAEINI
Acraea
encedon,
Blue Nile Falls,
Ethiopia
© Peter
Bruce-Jones
Introduction
There
are about 220 species in the genus Acraea, all
Afrotropical in distribution, with the exception of 3 species (
violae and issoria
from the Oriental region, and andromacha from Australia
& Papua New Guinea ). The vast majority of species are found in the forests and
savannahs of East Africa, while about 60 are found in West Africa.
All
Acraea species have elongate forewings and rounded hindwings. The wings
are thinly scaled and in many species are semi-transparent.
The scales wear off very easily so that insects more than 4 or 5
days old have a glassy or greasy appearance. The majority of species
have a predominantly brownish or greyish ground colour, marked with
bands or patches of red or orange. The basal area of the underside hindwings of most
species is marked with a pattern of small black spots. In many, including
encedon, these spots also appear on the upper
surface of the wings.
Acraea
encedon is distributed from Gambia to Ethiopia, Sudan and s.w. Arabia.
It's range extends south to
Angola, Malawi, Tanzania and Mozambique, and the butterfly also occurs in
Madagascar.
This species is
very similar to encedana, but has 2 black spots in
the discal cell of the hindwing whereas encedana
has only one spot. Both species produce colour variants - e.g. in Ethiopia and
Sudan the apical bar and hindwings of encedana are
pale orange, but elsewhere they are usually white. In
encedon the apical bar and hindwings in most parts of it's range are a
dull dirty orange, but in the mid-elevation Ethiopian form they are a very pale
orange.
Habitats
This
is a common species found in open savannah country, and can also be seen in
cleared areas within the forest zones, and on coastal grasslands and dunes.
Lifecycle
The larval foodplants include
Commelina ( Commelinaceae ),
Aeschymonene ( Papilionaceae ) and Pouzolzia
( Urticaceae ). On rare occasions
Desmodium salicifolium ( Fabaceae ) may be used.
Adult behaviour
Acraea encedon,
and it's very close relative encedana,
are particularly fascinating because both commonly produce
all-female broods. Typically over 50% of all broods of
encedon are all-female, but a study
in Sierra Leone revealed that no less than 95% of the broods
analysed were entirely female. The dominance of females has been
found to be caused by the selective killing of male embryos by a
Wolbachia bacterium
( Jiggins, 1998 ).
|
