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Butterflies of
the Amazon and Andes
Ellara Glasswing
Ithomia ellara
HEWITSON, 1855
Family -
NYMPHALIDAE
subfamily - DANAINAE
Tribe - ITHOMIINI
Ithomia ellara.
Introduction
The Ithomiinae 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.
Ithomiines
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.
Ithomiines are
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.
There 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.
Most novices find the Ithomiinae 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.
The Ithomia
Glasswings include
patilla, terra, arduinna
and ellara,
all of which have slightly bluish translucent wing membranes, and
veins which are outlined in orange on the underside, and with
black on the upperside. Males of Ithomia
have a distinctive blister on the costa of the underside hindwings
that corresponds with a patch of androconia ( pheromone producing
scales ) on the upper surface.
Ithomia ellara
is found from southern Ecuador to Bolivia.
Habitats
Butterflies in the genus Ithomia
are migratory, and occur in rainforest and cloudforest at elevations between sea
level and about 2000m. They spend much of the time deep in the
forest, but emerge in early morning or in overcast weather to
visit flowers along roadsides and riverbanks.
Lifecycle
I have no data regarding the early stages, but these are likely to be similar
to other members of the genus, as described below :
The eggs of Ithomia
are typically white, and laid singly on
the underside of leaves of
Witheringia,
Solanum, Acnistus
and other Solanaceae.
These
foodplants are highly toxic to
birds and other small vertebrates. At one time it was
thought that the chemicals within them
were accumulated by the larvae,
and passed on to the adult butterflies,
rendering them highly distasteful to birds.
Research by Edgar et al
in the 1970's and 80's however revealed that the alkaloids found in adult
Ithomiines and Danaines is sequestered from flower nectar and plant exudates,
rather than being derived from the larval foodplants.
The
caterpillars are
greenish and devoid of filaments but have a row of lateral
tubercles. The head is pale green, marbled with blackish.
The pupa is chrome-silver, and suspended by the cremaster
from leaves and stems. From a distance it can be mistaken for a droplet of
rain.
Adult behaviour
In cloudforests the
adults are attacked by Ceratopogonid midges, which feed on the
blood in the butterfly's wing veins and eyes.
Like other Ithomiines, the
butterflies spend long periods at rest on the foliage of small
shrubs in the darkness of their rainforest and cloudforest
habitats. They are extremely nervous, and if disturbed fly
immediately, only to resettle on another nearby leaf. The flight
is very slow, with characteristic deep wing beats. When feeding
in the open they behave very differently - both sexes being very placid and
reluctant to leave their flowers.
Males sequester pyrrolizidine alkaloids from
Heliotropium, Tournefourtia,
Myosotis ( Boraginaceae ), Eupatorium,
Neomiranda
and Senecio ( Asteraceae ). These
chemicals confer toxic qualities to the butterflies which deter
bird attacks. The chemicals are also used in the production of
pheromones. Often the males of several
Ithomiine species will gather together at communal leks, where they release
these pheromones from hair-like androconial scales on the leading
edge of their upperside hindwings. These attract more males, which
in turn release
further pheromones. After a few days the lek may include 50 or
more adults comprised of as many as dozen
different species. Passing females are attracted to the
leks by the complex fragrances. Their presence stimulates the
males to open their wings and release further pheromones that
entice them into copulation. Females obtain sustenance from
nectar, and also visit bird droppings which provide them with a
source of nitrogen that assists with the development of their
eggs.
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