On the Wings of Butterflies

Butterflies each have four wings, two fore wings and two hind wings that are attached to segments of the butterfly thorax. These wings are complex and highly-developed structures, delicate yet capable of supporting butterflies for thousands of miles of flight if necessary. Here's a closer look at the make-up of butterfly wings.

Veins
Wings are composed of two fine chitonous or membrane layers which are supported and nourished by veins that run throughout the wings. The pattern of these veins is different for every genus of butterfly and this difference is used by entomologists to help classify and recognize butterflies that may look similar but are actually not closely related. In the microscope photo below of a Polyphemus Moth wing, you can see the clear membrane with a vein running through it, bordered by scales.

Scales
Butterflies and moths belong to the order Lepidoptera, a name meaning "scale- wing" in Latin.These tiny scales are not very noticeable to the eye when looking at a whole butterfly wing, but if the wing is touched you will find a fine colored dust left behind. That dust is actually the tiny scales that cover the wings of the insect.

Individual wing scales of a Giant Swallowtail, magnified 30x.

Individual wing scales of a Giant Swallowtail, magnified 250x.

Tiny sockets in the membranes hold in the individual wing scales which give further support to the wings. In butterflies, these scales overlap in orderly rows just like shingles on a roof. Much like shingles, removing a bunch of them is a bad idea. Without the support of the wing scales, butterfly wings are not as structurally sound and are more likely to break. They are already delicate creatures, so losing that kind of support to their mode of transportation isn't so good for them.

Giant Swallowtail wing scales in place on the wing. (Magnification 250x)

The ridges in our fingerprints and the oils in our skin are more than enough to pry these wing scales loose with even the lightest of touch. If the scales are removed from both sides of the wings, you will find yourself with a somewhat brittle and transparent wing. Yes, you really can see right through it when the scales are rubbed off. Once removed, these scales will never grow back. Older butterflies will often lose scales to natural attrition, and their wings will appear duller or as if they have tiny pinpoint holes covering them just from the loss of scales.

These tiny wing scales plug into equally tiny sockets on the wings and are individually colored to create the incredible wing patterns which are so appreciated by human observers. The shapes, pigmentation and structures of each wing scale differ greatly. Some scales are structured in such a way that they refract light rays and can appear iridescent or as different colors from different angles which is very similar to LED lights.

Some butterfly scales are very specialized. Androconia are a specialized scales on male butterflies that are scented to help attract mates during courtship. The tiny hairs that can be seen on a butterfly's head are actually scale that stand straight up and just look like hairs.

Patterns: The patterns on the wings of a butterfly serve several purposes. The colors and shapes help butterfly to identify members of their species as possible mates or even as intruders in the territory of a particular male butterfly. Bright colors can warn predators that a butterfly species may be toxic when ingested. Some species have coloring and patterns on their wings that help them to camouflage in their surroundings and hide from prey.

Giant Swallowtail wing, 30x magnification

Thermo-regulation: Dark colors on a butterfly wing can act a bit like solar panels, absorbing heat and warming the haemolymph (blood) of the butterfly. When a butterfly needs more warmth they will rest in a sunny place with their wings open and bask in the sunlight. Butterflies can also use their flight muscles to shiver their wings to help them warm up.

Flight: Different wing shapes help butterflies fly in different ways. Skippers have triangular fore-wings which help them spring quickly into flight. Larger rounder wings make for a flight that involves a lazier style and gliding. Some butterflies can fly up to 10,000 feet and around 3,000 miles in their lifetime, using only their incredibly delicate wings.

Hearing Organs: Some butterfly families including Heliconius butterflies, known also as Longwings, have a specialized organ on their wings that works somewhat like an ear. This organ is a fluid filled sac covered with a thin membrane. High frequency sounds will cause the membrane to vibrate and send signals to the butterfly’s brain. Some butterflies are even able to differentiate between high and low pitch sounds which may help them with locating other members of their species or to avoid predators. The wide veins at the base of the fore wings contain nerve cells similar to those found in the hearing organs. Some species have good enough hearing abilities that they will react the the crunch of leaves under your feet as you approach them or take flight in response to the click of a camera shutter.