Butterflies of the
Amazon and Andes
Family - NYMPHALIDAE
subfamily - DANAINAE
Tribe - ITHOMIINI
cloudforest, 1700m, 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.
Ithomia is believed to have evolved
between 12-16 million years ago, at a time when the Andes were only
about half their present height. The evolution of the individual
species was probably a consequence of a major uplift in the Andes.
This created a massive diversification of microclimates and
habitats, thereby providing the stimulus for speciation.
Most of the 22
Ithomia species have
slightly bluish translucent wing membranes. They also have a small
tuft of orange scales just behind the head. This orange tuft is also
found in Napeogenes and
Aeria, but whereas
Ithomia have a bluish translucence,
Napeogenes are noticeably greenish, and
Aeria are a slightly opaque greenish
is found from Costa Rica to Bolivia.
inhabits cloudforests at elevations between about 1000-2000m. The
butterflies spend much of the time deep in the forest, but come out
into the open early in the morning or in overcast weather to visit
flowers along roadsides and riverbanks.
The eggs of Ithomia are typically
white, and laid singly on the underside of leaves of
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 are sequestered
from flower nectar and plant exudates, rather than being derived
from the larval foodplants. Ithomia
caterpillars are generally greenish and devoid of filaments but have
a row of lateral tubercles. The pupae are chrome-silver, and
suspended by the cremaster from leaves or stems. From a distance
they can be mistaken for droplets of rain.
All males in the tribe Ithomiini release
scent ( pheromones ). These serve a dual role - firstly to lure
and seduce potential mates, and secondly to act as a chemical
defence, a "nasty smell" to warn predators that they are
unpalateable and contain toxins. The toxins are primarily
derived from the caterpillar's foodplants Solanaceae, but are
supplemented by pyrrolizidine alkaloids sequestered by the
adults from fluids imbibed from the flowerheads and stems of
Heliotropium, Senecio and
various other plants.
In Ithomia males
these pheromones are stored within a reservoir which forms a
distinctive black blister just below the costa on the underside
hindwings. This reservoir corresponds with a patch of long
hair-like androconial scales on the upper surface. These "hair
pencils" disseminate the pheromones and are erected during
courtship, or when the males are displaying at a lek.
Ithomiine leks sometimes comprise of just a
few males of a single species, but often occur as aggregations
of up to 20 or 30 males of various Ithomiinae species. A long
established lek may include a dozen or more species. Leks are
often located in the vicinity of small streams in deeply shaded
parts of the forest.
Passing females are
attracted by the complex fragrances, and their presence
stimulates the males to open their wings and release further
pheromones that entice the females into copulation.
cloudforests the adults are attacked by Ceratopogonid midges, which
feed on the blood in the butterfly's wing veins and eyes.
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.
sequester pyrrolizidine alkaloids from
Myosotis ( Boraginaceae ),
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.
sexes, but in particular the males, are also carrion feeders, and can
often be seen imbibing bodily fluids from the decomposing corpses of
flies, spiders and other invertebrates. However, unlike certain other
Nymphalidae ( e.g. Apatura,
) they are not attracted to the carrion or dung of vertebrates.