Butterflies of the
Amazon and Andes
Family - NYMPHALIDAE
subfamily - DANAINAE
Tribe - ITHOMIINI
Oleria onega crispinella, Satipo, Peru ©
The Ithomiini comprises of 376 known species,
although it is likely that at least another 30 will be discovered in
the near future. All are confined to the neotropical region.
are unpalatable to birds, and are consequently mimicked in
appearance by many other species. These include other unpalatable
species ( Müllerian mimics ), not only from the Ithomiinae but also
from several other butterfly families. There are also a large number
of edible species ( Batesian mimics ) which have evolved similar
patterns. Birds have the ability to memorise butterfly patterns and
so learn to avoid eating noxious species, but are also fooled into
ignoring similarly marked edible species.
characterised by having small eyes, slender abdomens and long
drooping antennae that lack distinct clubs. Males have a plume of
long androconial scales or "hair pencils" on the costa of their
hindwings. These are hidden from view when the butterflies are at
rest, but are displayed when the wings are held open during
courtship. Other Ithomiine characteristics include a very slow and
deep wing beat, and a preference for inhabiting the darkest recesses
of the forest understorey.
are basically 2 types of Ithomiine. The first type are the black and
orange-banded "tigers", many of which are mimicked by other species
due to their unpalatability to birds. The second type are the
"glasswings", recognised by their transparent or translucent wings,
prominent veins, and orange wing margins. Many genera contain
examples of both of these types, and in some cases an individual
species may produce adults of both forms according to location.
novices find the Ithomiini very difficult to identify. Using only
the patterns to identify species is very unreliable because there
are so many similar species. Also many species produce a variety of
different colour forms according to locality and season. The best
approach therefore is to use the hindwing venation and other
anatomical features to identify the genus, and to then look at the
wing patterns to short-list the likely species.
Oleria comprises of about 50 known
species, recognisable from the distinctive venation of the
butterflies are varied in their habitat requirements - most species
occur in lowland rainforests, many others specialise in cloudforest
habitats, and a few occur in deciduous forests.
Oleria onega is
found from Colombia to Peru and s.w. Brazil.
is associated primarily with wet tropical rainforest habitats, and
is most often found in shady damp areas in the vicinity of rivers or
streams, at altitudes between 200-800m.
In common with all
other Ithomiines, females of Oleria onega
normally lay their eggs directly on the underside of leaves of their
foodplants. In the case of onega the
preferred foodplant is Solanum mite,
although other species including S. anceps,
S. angustialatum and
S. uleanum are also used.
eggs are white, oval, and laid singly, although several may be
dotted about in close proximity by one or more females. The eggs
hatch after about 3 days.
When newly hatched the caterpillar is
transparent. It consumes its egg shell before beginning to feed on
the foodplant. After each moult it consumes its shed skin, leaving
only the chitinous head capsule remaining. When fully grown it is
grey with a yellow line along the length of the body on each side.
It takes only about 12 days from hatching to being ready to pupate.
chrysalis is pale green with shiny metallic golden reflections. The
abdominal segments are compressed, and there is a dorsal hump. The
overall impression is of a small leaf dripping with rain. The
butterfly emerges after about a week.
The lifecycle from
egg to adult takes about 3 weeks to complete, so in theory up to 17
generations could be produced annually. However during the dry
season reproductive activity is minimal. During this period the
adults aggregate with numerous other Ithomiine species in small
pockets within the forest. In Brazil and Ecuador for example I have
found several such aggregations along the beds of small dry streams,
where as many as 100 Ithomiines of up to 10 different species could
be found aestivating among the stilt-like rootlets of palms.
In 2002 Gallusser published research
findings following a study of 2
onega subspecies found near
Tarapoto in Peru. The two colonies are very close to each other,
O. onega agarista
being found on the relatively cool wet NE
slope of the Cerro Escalera mountain range, while subspecies
"ssp. nov" ( as yet unnamed ) is found on the hot sunny SW
onega agarista behaved as expected,
always laying their eggs on Solanum;
ssp. nov laid them instead on rocks, stems, dead leaves and
other substrates up to a metre distant from the foodplants.
that the different oviposition strategy was influenced by egg
predation, and found that the main threat came from
ants, which were common on the SW slope, but entirely absent
from the NE slope. She also noted that partial deforestation and
path clearance on the SW slope allowed more sunlight to
penetrate, so that eggs laid on
Solanum in these situations would
be easier for predators to locate. The implication is that ssp.
nov is evolving different egg-laying behaviour as a direct
result of human interference in its habitat.
As part of the research, Gallusser moved
eggs from one site to another, and from one substrate to
another, and studied the survival rates of 400 eggs on both
mountain slopes. She found that on the SW slope, eggs positioned
away from Solanum
had a much higher survival rate than those on
the plants. Laboratory and field studies
however failed to provide observations of predation, even when
the eggs were offered directly to the ants, so it seems possible
that the mere presence of
the aggressive ants on the foodplants may be enough to
discourage the females from ovipositing, forcing them to lay
adults are normally found in small "leks" of up to a dozen
The males fly very slowly
and almost incessantly around the lek area, only pausing to settle for
a moment here and there, at which time they slowly fan their wings,
probably to aid dissemination of pheromones from the androconial
"hairs" on their wings.
of most Oleria species visit
Eupatorium, from which they acquire
pyrrolizidine alkaloids which they pass to the females during
copulation, and which is believed to be essential for the production
of viable eggs.
visit various flowers for nectar and pollen - the latter may be
essential in the production of eggs and the maintenance of ovaries, as
has been demonstrated to be the case with Heliconiines. Females also
receive proteins during sperm transfer.
Gravid females fly very slowly,
periodically dipping down to investigate Solanum
plants. Having found the foodplant they then spend 2 or 3 minutes
testing it, using olfactory sensors on their legs, antennae and
abdomens, to determine whether it is Solanum
mite or another related species.
common with most other Ithomiines, lateral and altitudinal migrations
of Oleria species are triggered by
seasonal changes in humidity.