The "mechanical engineering" of a butterfly wing scale

[Beatsy]

OK, it's only a 0.25mm long butterfly wing scale, but for such a tiny thing the precision and "design" efficiency is amazing.

Scales are modified hairs, grown by sloppy, wet biological processes that somehow make consistent regular structures while conserving material and reducing weight (by reinforcing just enough for each area). Iridescent wing scales also have nano-scale structures that produce colours by interference - but not here as this one is only pigmented.

Note how the "ladder rungs" are closer together near the stalk with random orientation for extra strength where the stalk joins the main body of the scale. Near the middle, where stress is lower, far fewer rungs are present but they're up to twice as dense at the sides and end - to add rigidity and strength to these potentially vulnerable areas.

Yet all this "clever engineering" and optimisation emerges from natural selection over countless generations. It's hard to think up what selection pressures could contribute to developing these parts, but the mystery only adds to their allure for me. Thought-provoking things!

The image is a focus stack shot in bright field illumination with an Olympus UPlanSApo 100x/1.4 and Sony A7riv running in APS-C crop mode (26 megapixels). Condenser and objective oiled to the slide.

[gewo]

top work

[anne]

Hi Steve,
I think the brown dots are the pigments, the Melanin.
Wonderful resolution.
best
anne