handsome genus Heliconius, the others
being species of the genera Mechanitis, Melinaea, or Tithorea, though
several species of other Danaoid genera also imitate each other. The
following lists will give some idea of the number of these curious
imitative forms, and of their presence in every part of the Neotropical
area. The bracketed species are those that resemble each other so
closely that the difference is not perceptible when they are on the
wing.

In the Lower Amazon region are found--

{ Heliconius sylvana.
{ Melinaea egina.

{ Heliconius numata.
{ Melinaea mneme.
{ Tithorea harmonia.

{ Methona psidii.
{ Thyridia ino.

{ Ceratina ninonia.
{ Melinaea mnasias.

In Central America are found--

{ Heliconius zuleika.
Nicaragua { Melinaea hezia.
{ Mechanitis sp.

{ Heliconius formosus.
{ Tithorea penthias.

Guatemala { Heliconius telchina.
{ Melinaea imitata.

In the Upper Amazon region--

{ Heliconius pardalinus.
{ Melinaea pardalis.

{ Heliconius aurora.
{ Melinaea lucifer.

In New Grenada--

{ Heliconius ismenius.
{ Melinaea messatis.

{ Heliconius messene.
{ Melinaea mesenina.
{ (?) Mechanitis sp.

{ Heliconius hecalesia.
{ Tithorea hecalesina.

{ Heliconius hecuba.
{ Tithorea bonplandi.

In Eastern Peru and Bolivia--

{ Heliconius aristona.
{ Melinaea cydippe.
{ (?) Mechanitis mothone.

In Pernambuco--

{ Heliconius ethra.
{ Mechanitis nesaea.

In Rio Janeiro--

{ Helieonius eucrate.
{ Mechanitis lysimnia.

In South Brazil--

{ Thyridia megisto.
{ Ituna ilione.

{ Acraea thalia.
{ Eueides pavana.

Besides these, a number of species of Ithomia and Napeogenes, and of
Napeogenes and Mechanitis, resemble each other with equal accuracy, so
that they are liable to be mistaken for each other when on the wing; and
no doubt many other equally remarkable cases are yet unnoticed.

[Illustration: FIG. 25.--Wings of Ituna Ilione, female. Wings of
Thyridia megisto, female.]

The figures above of the fore and hind wings of two of these mimicking
species, from Dr. Fritz Mueller's original paper in _Kosmos_, will serve
to show the considerable amount of difference, in the important
character of the neuration of the wings, between these