Mexico, USA & Canada
Family - NYMPHALIDAE
subfamily - DANAINAE
Tribe - ITHOMIINI
subtribe - MECHANITINA
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.
The genus Mechanitis
contains 4 medium-sized species, all of which bear superficial
similarities to various members of other genera, including
Tithorea and Forbestra, which
have similar "tiger" patterning in black, orange and cream. All
these species ( and other smaller Ithomiines that have similar
patterns ) are toxic or unpalateable to birds. The shared pattern
gives the butterflies an "advantage in numbers" because
insectivorous birds learn to avoid all "tiger" species - tasting one
such butterfly causes birds to vomit, and the experience is enough
to convince them to leave similar looking creatures alone.
The similarity of colour and pattern doesn't only
fool the birds - it also makes it difficult for human observers to
distinguish the species. In the case of Glasswings it is relatively
easy to determine the genus by examining the venation, particularly
that of the hindwings. It is difficult to make out the venation on
Tiger-mimics however so you need to learn how to recognise other
diagnostic features. These include wing shape, antennae length /
colour, and the position and shape of particular spots in the discal
and apical parts of the wing.
is a very widespread species, distributed from southern Mexico to
Mechanitis lysimnia is found in
disturbed forest habitats in Central America and on both sides of
the Andes, at altitudes between 0-1500m.
The whitish barrel-shaped eggs are laid in batches of between 10-50
under the leaves of Solanum and
possibly other members of the Solanaceae. The larvae are gregarious.
When fully grown they are pale green streaked with yellow, and have
a series of tubercles projecting below the spiracles. The chrysalis
is silver with brown streaks on the wingpads and abdomen.
butterfly is visible mainly in the early morning, and again in late
afternoon, at which time the females can be found visiting
Eupatorium flowers in forest clearings
and along riverbanks. Males, in common with other Ithomiines, form
"leks" to which the females are attracted by pheromones. The
pheromones are disseminated by males from "hair pencils" - special
androconial scales located, in the case of
Mechanitis, on the costa of their upperside hindwings. These
can be seen protruding in the photograph of the ambushed example at
the top of the page.
In seasonal rainforests, where there are
pronounced wet and dry seasons, Mechanitis
gather to aestivate during the dry season at the few remaining damp
areas of the forest, typically in gullies or along the beds of
streams. Such places often have 100s of Glasswing and Tiger-mimics
Ithomiines in residence for up to 3 months towards the end of the dry
© Adrian Hoskins