Peeking Into a Chrysalis, Incredible Videos Capture Butterfly Wings Forming During Metamorphosis - SciTechDaily

If you brush against the wings of a butterfly, you will likely come away with a fine sprinkling of powder.

Now, MIT engineers have captured the intricate choreography of butterfly scales forming during metamorphosis.

The team has for the first time continuously observed the wing scales growing and assembling as a developing butterfly transforms inside its chrysalis.

With some minor surgery and a clever imaging approach, the researchers were able to watch wing scales form in specimens of Vanessa cardui, commonly known as the Painted Lady butterfly.

They observed that, as a wing forms, cells on its surface line up in orderly rows as they grow.

SEM imaging is typically used to visualize the developing scales on a butterfly wing (two individual scales shown, top left); a new approach uses quantitative phase imaging to show individual scales in more detail (top right and bottom).

“Butterfly wings control many of their attributes by precisely forming the structural architecture of their wing scales,” says lead author Anthony McDougal, a research assistant in MIT’s Department of Mechanical Engineering.

Knowing what processes butterflies harness to grow their scales could help to further direct this kind of bioinspired technology development.

Currently, what’s known about scale formation is based on still images of developing and mature butterfly wings.

In their new study, he and his colleagues looked to continuously observe how scales grow and assemble in a living, morphing butterfly.

They chose to study specimens of Vanessa cardui, as the butterfly’s wings have features that are common across most lepidopteran species.

Once each caterpillar encased itself in a chrysalis, indicating the beginning of its metamorphosis, the researchers carefully cut into the paper-thin material and peeled away a small square of cuticle, or covering of the developing wing, exposing the scales growing underneath.

They then used a bioadhesive to stick a transparent coverslip over the opening, creating a window through which they could watch as the butterfly and its scales continued to form.

A depth scan through the wing scales of a pupa that has completed 83% of its metamorphosis.

In their visualizations of the growing butterfly wing, the team watched the formation of highly detailed features, from micrometer-sized scales to even finer, nanometer-high ridges on individual scales.

They observed that, within days, cells quickly lined up in rows, and soon after differentiated in an alternating pattern of cover scales (those overlying the wing) and ground scales (those tucked underneath).

Scientists had assumed these grooves were a consequence of compression: As scales grow, they were thought to squeeze in like an accordion.

But the team’s visualizations showed that instead of shrinking as any material would when compressed, the scales continued to grow in size as ridges appeared on their surface.

The group hopes to explore this, and other processes in the developing butterfly wing, which can help to inform the design of new functional materials.

And on the surface, scales are forming, along with features on the scales themselves.