Photonic Structures in Nature - Bionanotechnology: Global Prospects - page 505

in.that.they.frequently.produce.color.through.a.3D.photonic.crystal..Since.these.3D.crys-
tals.potentially.manipulate.the.low.of.light.in.all.directions.by.the.production.of.partial.
photonic.band.gaps,.these.structures.represent.one.of.the.most.advanced.photonic.systems.
observed.in.structural.color.production.

25.2.1 Eupholus magnificus and Eupholus schoenherri pettiti

The.weevils.of.the. Eupholus .genus.are.herbivorous.beetles.from.the.Curculionoidea.family.
and.have.all.the.hallmark.characteristics.of.other.insects.of.the.order.Coleoptera,.although.
the.morphology.is.slightly.different.from.that.of.other.beetles.in.that.the.head.is.elongated.
into.a.snout.and.the.legs.are.proportionally.longer.when.compared.to.the.abdomen..As.
with.all.beetles,.weevils.have.four.wings,.two.of.which.are.light.wings.and.the.other.two.
forming.a.hard.protective.shell,.the.elytra..The.iridescent.colors.displayed.by.these.beetles.
are.typically.generated.in.extracuticular.scales.that.cover.the.majority.of.their.bodies,.with.
the.underlying.cuticle.appearing.virtually.black,.greatly.increasing.the.apparent.vibrancy.
of.the.scales.
When.removed.from.the.beetle.and.imaged.under.an.optical.microscope.in.relection.
and. transmission. (Figure 25.7a. and. b,. respectively),. it. was. observed. that. colors. of. indi-
vidual.scales.in.relection.and.transmission.were.complementary,.which.is.consistent.with.
the.presence.of.only.minor.absorption..Manipulation.of.these.images.to.evaluate.the.color.
of.absorption.demonstrated.a.total.hue.consistent.with.the.presence.of.a.small.amount.of.
melanin.within.the.cuticle.of.the.scale.
On.illuminating.the.scale.with.linearly.polarized.light.and.observing.with.a.crossed.lin-
ear. analyzer,. domains. that. demonstrated. a. relection. of. shorter-wavelength. light. were. still.
brightly.colored,.which.would.only.be.observed.through.the.rotation.of.the.polarization.vector.

(a) (b) (c)

(d) (e) (f )

FIGURE 25.7
(See.color.insert.).White.illuminated.microscope.images.to.show.the.(a).relection.and.(b).transmission.colors.of.
a.single.scale.from.the.blue.region.of. E. magniicus ..This.scale.was.selected.to.show.the.large.size.of.the.domains.
within. these. scales,. and. the. consistency. of. the. hue. that. they. produce.. By. comparison,. the. scales. from. other.
regions.demonstrate.multiple.domains.and.colors.(see.Figure.25.9)..(c-f).Four.images.of.domained.scales.from.
other. regions:. (c). yellow. region,. E. schoenherri pettiti ;. (d). green. region,. E. schoenherri pettiti ;. (e). blue. region,. E.
magniicus .(dark.ield.image);.(f).green.region,. E. magniicus ..Scale.bars:.30.μm.