Butterflies of
the Amazon and Andes
Antisao Glasswing
Pteronymia sao
HÜBNER, 1813
Family - NYMPHALIDAE
subfamily -
DANAINAE
Tribe - ITHOMIINI
subtribe -
DIRCENNINI
introduction
|
habitats |
lifecycle |
adult behaviour
Pteronymia
sao, Satipo, Peru
Introduction
The
Ithomiine Glasswings are amongst the most difficult butterflies to identify, as
all seem to have fairly similar patterns, with wings transparent except for dark
veins, a white subapical band, and orange margins. To make matters worse, there
are also members of the Pieridae ( Dismorphiines ) which mimic the butterflies
very well, and breed in the same habitats.
The Dismorphiines can be eliminated as candidates by simply counting the
butterfly's legs - they have 3 pairs of legs, whereas Ithomiines have only 2
pairs.
The
next step is to establish the genus, reasonably easy for an expert
lepidopterist, as the venation ( the layout of the wing veins ) is different
with each genus. Fortunately the venation of Glasswings is easy to see, due to
the transparency of the wings.
Having established the genus, it is then a matter of examining the layout of the
white spots and orange borders to establish the species.
The
genus Pteronymia
contains 46 known species, many of which are very similar to the illustrated
insect, although some such as
donella, picta
and lonera
are more heavily marked and have orange hindwings.
This butterfly is also known by
the junior synonym antisao.
It
occurs in the Upper Amazonian region from Brazil to southern Peru and Bolivia.
Pteronymia
sao, Mariposa, Satipo, Peru
Habitats
Pteronymia sao
breeds at altitudes
between about 200 - 1600m in wet primary rainforest and transitional cloudforest
habitats.
Lifecycle
The precise details are unknown, but the following applies in general to
butterflies in the genus
Pteronymia
:
The
eggs are white, and laid singly on the underside of leaves of Solanaceae.
Females of most species return several times to the same plant, laying up to a
dozen eggs in total.
The
larvae of Pteronymia
species vary in appearance, some being dark along the back, with a pale central
stripe, while others are banded in black and white, and characterised by the
presence of a pair of soft fleshy horns projecting forward from the first
thoracic segment.
The
pupae of this genus are typically squat in shape, with compressed abdominal
segments, and a bulbous thoracic section. They are generally silver or gold in
colour, shiny, and resemble large raindrops hanging from stems or the undersides
of leaves.
Pteronymia
sao, Mariposa, Satipo, Peru
Adult behaviour
The butterflies are usually encountered singly, flying in deeply
shaded areas of the forest understorey. Like other Glasswings,
they tend to spend long periods stationary, perched on foliage in
light gaps. When disturbed they fly rapidly, but with slow
wing-beats, and resettle a short distance away, usually higher up,
but tend to return to their home ground within a few minutes.
Males visit the
stems of Eupatorium and
Heliotropium plants, from which
they acquire pyrrolizidine alkaloids which they convert within
their bodies into pheromones. They gather, together with males and
females of various other Ithomiine species, at "leks", where the
males of each species release their pheromones, which are
disseminated via "hair pencils" of androconial scales on the
wings.
This behaviour
attracts more males and females of each species, until upwards of
a 20 butterflies are present. It is believed that females may be
able to assess the alkaloid content of a male, and may elect to
mate with the male with the highest concentration. The alkaloids
are probably then transferred to the female during copulation,
implying that males with high concentrations are essential for the
production of fertile and viable eggs by the female. Other studies
have demonstrated that the alkaloids also function as toxins to
deter avian predators.
Females do not
acquire the alkaloids from plants, but do visit
Eupatorium and various other
flowers for nectar and pollen, and also visit the droppings of
ant birds and ant wrens, from which they obtain nitrogen compounds.
Pteronymia, like most Ithomiines,
demonstrate strong seasonality, being most abundant at the
beginning of the rainy season. In the transition period between
seasons they show a tendency to migrate, both laterally and
altitudinally - a behaviour that is probably linked to the
movement of the ant swarms, and thereby to the location of the
ant birds and ant wrens that follow them.
Pteronymia
sao, Mariposa, Satipo, Peru
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