1 - Head
2 - Thorax - legs & abdomen
3 - Wings
venation & scales
- Wing scales - scanning electron microscope images
- Hearing organs, flight,
A female Brimstone
Gonepteryx rhamni, seen here extending
it's proboscis to suck up nectar from a thistle flower. The
pattern of raised wing veins ( venation ) can be seen clearly ©
butterflies and moths ( except Plume moths ) have 2 pairs of
overlapping wings, each comprised of a very thin double membrane
with rigidity supplied by a network of tubular veins which radiate
from the base of the wings. The pattern of veins is different for
every genus of butterfly, and is one of the main criteria used by
taxonomists when classifying butterflies.
structure of a transparent Satyrine butterfly
Haetera piera © Tony
The wing membranes are
transparent, but are partially or fully covered in a dust-like layer
of tiny coloured scales. Each scale comprises of a flat plate arising
from a single cell on the wing surface.
The scales vary
considerably in shape, some being rectangular, while others are shaped
like tear-drops or plumes. An individual scale might typically measure
about 50 microns across ( 1/20 of a millimetre ) and be 100 microns
long, although many are hair-like, and are very much longer.
There can be as many as 600 individual scales per sq millimetre of
wing surface, although in certain genera such as
Acraea, Aporia and
Parnassius the density is considerably
lower, giving the wings a translucent appearance. In some tropical
genera such as Ithomia,
Cithaerias the scales are absent from large areas of the wings,
resulting in almost complete transparency.
( Peru ), wing scales, magnification x10 ©
There a 3 basic types of
scale - pigmentary scales, structural scales, and androconia.
are mostly flat. Their colour is the result of the presence of
melanins, pterins and other chemical pigments, most of which are
sequestered from the larval foodplants and passed to the adult
butterflies. The pigments account for the basic colours found in
butterfly wings - black, red and yellow. The juxtaposition of the
various coloured scales, and the amount of pigment they each
contain, can create the illusion of additional colours such as
orange, cream and green.
In some species such as
the Orange tip Anthocharis cardamines
the mottled green markings on the underside are an illusion caused
by having a finely balanced mixture of yellow and black scales.
Subtle variations in scale pigmentation and density can create
illusions such as texture or shading, which help to give the wings
of some butterflies a 3-dimensional appearance.
scales are also known as "ground scales" as they effectively form a
lower ground layer of colour and pattern on a butterfly's wings. The
scales are laid out in neat rows like the tiles on a roof. Each row
comprises of alternating pigmentary and structural "cover scales".
The latter are larger than the pigmentary scales. They overlap them,
and are semi-transparent so the colours of the pigmentary scales can
be seen through them.
Structural scales. The
fiery hues of
Lycaena Coppers, the golden-yellow of
Troides Birdwings, the glittering
metallic greens of Caria Metalmarks
the dazzling blues of the South American
Morpho butterflies are produced by the refraction,
diffraction and interference patterns of light as it strikes or
passes through the semi-transparent structural scales.
case of diffraction
light is broken
up into lighter or darker bands after passing through a lattice of
microscopic bubbles or slits within the scales. Refraction on the
other hand is where light is broken up into its constituent rainbow
colours as a result of passing through prismatic ridges on the
surface of the scale. Interference patterns are the result of light
passing through clear layers of varying density, and being reflected
back in such a way that the colours change according to the angle of
view. Examples of such iridescent colour are found in many
butterflies, but are particularly striking in neotropical
Doxocopa butterflies, where a band of
colour can change from electric blue to vivid turquoise or dazzling
silver as sunlight strikes the wings at different angles.
is the Sunset moth Chrysiridia rhipheus,
in which the slightest change of angle causes metallic green bands
on the fore-wings to change to turquoise, while a contrasting patch
on the hindwings undergoes an even more dramatic change, cycling
through every colour in the rainbow as light hits it at different
angles. Its extraordinary brilliance and iridescence is due to its
curved ribbon-like scales, which cause light to bounce about between
adjacent scales rather than be reflected straight back to the
Almost all butterflies
and moths have a mixture of pigmentary and structural scales. In
combination these can produce any colour ranging from metallic gold
to fluorescent orange,
green, sapphire blue,
or any other colour seen
on butterfly wings. They can even display colours beyond the visible
spectrum - most butterflies, in addition to the colours and patterns
visible to humans and birds, also have a "hidden" ultra-violet
pattern that can only be detected by other butterflies.
found mainly on male butterflies. They usually exist as
slightly raised dark streaks or patches on the forewings, and often
have a mealy appearance. At the base of the androconia are tiny sacs
containing scent ( pheromones ). The scent is disseminated via tiny
hairs or plumes on the edges of the scales, and used to entice
females to copulate.
can also take the form of tufts ( e.g. on the hindwings of
Charaxes, or can be found in androconial folds such as found
on the hindwings of Papilionidae or the costal fold of Pyrginae. In
the Danaini and Ithomiini they occur as "hair-pencils". These can
either take the form of extrusible organs at the tip of the abdomen,
or occur as long "hairs" on the hindwings. In some species e.g.
Lycorea the abdominal organ is brushed
against androconia on the hindwings to collect pheromones. These are
later disseminated by expanding the tufts in the presence of
can also occur as "stink-clubs" in the genital opening of female
Ornithoptera and Heliconius
butterflies, and in certain moth families e.g. Saturniidae,
Lasiocampidae and Lymantridae.
dark diagonal patch
on forewings of the male
Large Skipper illustrated above are composed of hundreds of
androconial scales. These disseminate pheromones that can be
detected by females during courtship. As the male ages the strength
of his pheromones diminishes, thus by analysing the strength of the
pheromones a female can assess the age and virility of a potential
Plume moths from
the families Pterophorinae and Alucitidae have no wing membranes.
Instead their fore and hind wings each consist of rigid veins edged
with dozens of long thin feathery scales giving rise to the common
name of "plume moths".
There are 186 species of Alucitidae worldwide,
many of which have only been discovered in the last 20 years. The
name of the moth depicted below, Alucita
hexadactyla translates as "20 fingers" but is a misnomer:
Alucitidae actually have 24 feathery plumes ( some are hidden in the
image below ).
Hampshire, England ©
are similar anatomically but are distinguished by their long,
spurred hind legs and the odd resting posture in which the wings are
rolled up and held at an angle of 90° to the body.
Common Plume moth Emmelina monodactyla
( Pterophorinae ), England ©