In both butterflies and moths, wings are the primary locomotory organs. Wings in these flying creatures consist of two flattened, very thin, and hard proteinaceous membranes made of “chitin”. The wings contain veins, which originate at the base of the wing where the chitin membranes are attached to the musculature of the thorax (thorax is the region between the head and abdomen). This musculature aids in wing movement. Veins are hollow and filled with blood, they function in oxygen exchange, thereby aiding in breathing.
When a fully grown adult butterfly emerges out from the pupa, the wings are delicate and crinkled, un-inflated, and wet. Then the butterfly hangs up side down and pumps blood into the wings to inflate them. Once the wings are completely inflated and dried up, the insect is ready to fly. These wings lack the ability to self-repair if they are damaged or torn. Both butterflies and moths have four wings – two fore wings and two hind wings. During a flight, both the forewings and the hind wings are held together and function as a single wing. Furthermore, strong muscles in the thorax move the wing up and down in an 8 (figure eight) pattern.
The name “Lepidoptera” (Order) which includes both butterflies and moths originates from the Greek word which means “Scale Wing.” These wing scales are the tiny overlapping pieces of chitin on the wings of a butterfly or a moth. The front and back side of the wing usually differs in its pattern. Apart from being responsible for the magnificent colour in butterflies and moths, scales are also helpful in protecting the body by providing insulation and allowing the flow of air when the insects are in flight.
As butterflies are cold blooded animals, they depend on external sources for heat. This heat brings the core body temperature to levels suitable for proper body metabolism. In this context, scales may also help to soak up heat that is required for the insects’ flying. Several preliminary research articles suggest that even a small change in the thickness of the wing scales can impact the heat absorbing capacity of the scales to a large extent.
The scales may occur in various shapes and sizes like almost square, scythe shaped etc. Some of these scales may also contain complex pigments. These pigments give color to the wing and are responsible for the intricate matt coloration in many species. The glossy coloration is an artefact of light reflecting off uneven surfaces of scales with a very complex structure.
Though many butterflies and few moths are brightly colored, they often show other types of patterning which is visible to the human eye only under ultraviolet light. Other members of the species on the other hand, have no problem seeing these patterns. Male butterflies have a modification in the wing scales which are called ‘Androconia’ or scent scales. These scent scales are present on the fore wings and they release pheromones which attracts females of the same species, during the time of their mating.
The wing coloration serves several purposes like providing camouflage from predators by helping these insects blend into their environment and serving as warning coloration (aposematic). The latter can be explained thus – Brightly colored butterflies taste bad to predators in general, so by mimicking these ill tasting species, the other species can escape predation.
Some butterflies have large spots on their wings as though resembling eyes. These are called eye spots. These eyespots deceive the predator into thinking that the butterfly is a bigger animal, such as an owl. Also, as darker colours soak up heat faster, having dark colored wings help attain optimal core temperature faster.
Deepak Tarun is a post graduate in Zoology. Not one to embrace anything at its face value, Deepak believes in really digging to the roots, before arriving at a decision. A budding wildlife biologist and passionate knowledge seeker, Deepak likes to read, and watch stand-up comedy in his spare time.