Butterfly Wings: Structure, Color and Function
A butterfly has four wings, two forewings and two hindwings. They are attached to the second
and third thoracic segments (the meso-thorax and meta-thorax).
Strong muscles in the thorax move the wings up and down in a figure-eight pattern during flight.
When the fully-grown adult butterfly emerges from its pupa (chrysalis), its delicate wings are
crinkled, wet, and uninflated. The butterfly hangs upside-down and pumps blood into the
wings to inflate them. It must then wait for the wings to dry before it can fly.
When the fragile wings fray or are torn, they do not repair themselves.
Butterfly wings are made of two chiton layers (membranes) that are nourished
and supported by tubular veins. The veins also function in oxygen exchange (breathing).
Covering the wings are thousands of colorful scales, together with many setae
The name Lepidoptera (which includes butterflies and moths), means "scale wing"
in Greek. These wing scales are tiny overlapping pieces of chitin on a butterfly or moth wing.
The scales are outgrowths of the body wall and are modified, plate-like setae. The front and
back of the wings usually have different patterns.
Scent scales are modified wing scales on the forewing of male butterflies and
moths (on the costal fold) that release pheromones. These chemicals attract
females of the same species. Scent scales are also called androconia.
Many butterflies are brilliantly colored, while others are drab. There are often ultraviolet
patterns in the wings that we cannot see, but which may be seen by other butterflies.
Even many of the colorful species have drab-colored outer wings (that are visible when
the animal is at rest). The coloration of these insects serves many purposes
Camouflage, in which the color of the animal helps it blend into the environment, hiding the
insect. The Australian leafwing butterfly, for example, is shaped and colored like a leaf.
Warning (or aposematic) coloration: brightly-colored butterflies and moths are either bad-tasting
or a mimic of similar-looking bad-tasting butterflies.
Attracting and finding mates, who look for certain colors and patterns.
Deceiving predators into thinking they're bigger than they really are. Some wings have large
"eyespots" which make the butterfly or moth look like the face of a larger animal (like an owl),
scaring away some predators.
Soaking up heat: dark-colored scales soak up heat very well when the butterfly suns itself.
Like all insects, butterflies are cold-blooded. When they get too cold, they warm themselves
in the sun.
Butterflies actually get their colors from two different sources: ordinary color (or pigmented)
and structural color.
Basic Butterfly Wing Structure Showing Veins
The ordinary color comes from normal chemical pigments that absorb
certain wavelengths of light and reflect others.
For example, the pigment chlorophyll colors plants green. The chlorophyll soaks up the blue
and red colors of the spectrum, but not the green, which you see when it bounces back to
your eye. Most butterflies get their different shades of brown and yellow from melanin,
the same pigment that makes you tan in summer and gives some people freckles.
The structural color of butterflies is where things get interesting. This type of color stems from
the specific structure of the butterflies' wings and explains why some of a butterfly's colors
seem to shift and appear so intense. This quality of changing colors as you, the observer,
moves is known asiridescence. It happens when light passes through a
transparent, multilayered surface and is reflected more than once. The multiple reflections
compound one another and intensify colors.
During flight, the forewing and hindwing are held together and function as one wing. The
coupling mechanism differs in different species. In most butterflies, a lobe on the hindwing
presses against the forewing. In most moths, bristles on the front edge of the hind wings
(called the frenulum) connect with hooks on the hind edge of the forewing.
When at rest, butterflies hold their wings vertically. Moths hold their wings horizontally when
at rest. A monarch butterfly at rest is pictured to the right.
Butterflies and Moths of North America
Southern Wisconsin Butterfly Assn (NABA)
The Butterfly Site