|Photo: John Raffaghello|
Butterfly wings vary in shape, color and function. Everything about their wings
is genetically based allowing each species to be adaptive to their environments.
During the butterfly pupa stage is when wings are formed. They start as a double
layer of unpigmented epidermal cells.
In the later
the structural scales develop, forming butterfly colors and wing patterns.
Wings are made of membranes. Veins throughout these membranes provide nourishment and oxygen. Once the adult butterfly emerges from it's pupa it takes up to three hours for the soft, limp wings to fill with hemolymph, or blood, through these veins. After butterfly wings have filled with blood then they can fly.
On these membranes are overlapping rows of many little hairs called setae. Setae are more commonly called scales.
|Photo: Craig Taylor|
Tactile setae are are longer hairs attached to nerve cells on appendages such as antennae and mouth parts helping the butterfly to sense touch. All information through these nerve cells is relayed to the butterfly brain.
|(Tactile setae lower left) Photo: Photowitch|
All lepidoptera are the only insects to have scales on their wings,
which is why the literal translation of this term means 'scale-wings'.
The pedicel is the base of each individual scale that attaches to the membrane. Circling around the pedicel is a donut-like cell called a tormogen. Inside the tormogen at the pedicel base is a single cell called the trichogen. The trichogen produces a sex phermone secretion that also helps to flatten scales, allowing them to overlap like shingles on a roof.
The pedicel loosely attaches the scales to butterfly wings and they fall off easily. If we touch butterflies dozens of these scales fall off. It looks like powder. Although it doesn't hurt, scientists debate if these scales falling off harms the butterfly. Some believe no harm comes to the butterfly, while others believe in time, the more scales that fall off will impair the butterflies ability to fly well.
It isn't also agreed if there is a purpose for these scales to fall off so easily. One theory is if a butterfly flew into something sticky, like a cob-web, they can get out more easily and leave the scales behind.
As butterflies age it is not uncommon for their wings to become tattered, torn and the colors also can begin to fade. Once damage occurs, the wings do not repair themselves. This is because hemolymph does not flow throughout the entire wing, only the vein.
Below the picture on the left shows where scales have fallen off.
The picture on the right shows veins throughout the wings.
Butterfly wings are attached to muscle in the thorax region of the butterfly anatomy.
These muscles are strong! Wings are bilaterally symmetrical in shape and color.
|Photo: Howard Cheek|
This picture shows the location of the wings in the thorax. Consider the
proportion of the wings to the size of the muscles that are making those wings
Butterflies don't fly the same. Their wings are built differently and so are their bodies. For example, butterfly wings can be thicker, longer, shorter, angled or rounded. The wings of butterflies are relatively flat. With all of these creating different dynamics along with the force of gravity, each butterfly will fly differently.
Anterior margin (costal margin) is the long edge of wing closest to the head, or forewings are usually thicker giving wings a slight curve in flight. The same for their bodies.
Species with larger butterfly wings are able to use their wings on upward thrust getting them air bound more quickly. Larger wings also create thermal uplifts where they can glide for minutes. They don't require faster or multiple strokes to remain air-bound. They use their large wing to create a larger upward lift against gravity.
Smaller butterflies need lots of metabolic energy to create faster strokes to become air-bound. Their small wings require an upward force exceeding the downward pull of gravity.
The different sizes of butterfly wings will also dictate the number of flaps each species must make per minute to remain air-bound. Swallowtail Butterflies beat their wings relatively slowly, about 4-5 times a second. Monarch Butterflies, along with many others in the Danaidae Butterfly Family beat their wings anywhere between 5-12 times a second.
Other bits of information about the wings of
Video has Great cinematography and confirms these are flying machines.
When the butterfly is in flight they make a slanted circle-eight pattern. This is what we commonly call fluttering and is technically termed dodging. The angling of wings is done during circle-eight because the butterfly propels itself forward. Another butterfly pattern when in flight is hovering and flying in a backward motion.
This form of hovering requires a great deal of metabolic energy. Dodging is done to confuse hungry birds and other prey that may be watching.
Butterflies are equipped with aerodynamic mechanisms to generate force. Aerodynamics is the science that studies the dynamics of air motion, other gases and interaction with moving objects. With knowing butterflies have aerodynamic capabilities it should come as no surprise to learn that some species make long distance migratory flights.
As with so many other characteristics of different Lepidoptera species, there are exceptions when it comes to butterfly wings.
Not all wings are made completely of scales. This picture above left is of a Greta-Oto Butterfly, also known as a Glasswing butterfly.
The Glasswing butterfly wings are the transparent membrane only. These membranes underly all butterfly and moth wings.
The Danais Tytia Butterfly upper forewing shows the membrane only.
Both the Greta-Ota
and Danais Tytia are
from the Nymphalidae,
or Brushfooted Family.
|Photo: Valeriy Kirsanov|