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Beetle Shine
When actress Ellen Terry stepped onto
the stage at Lyceum Theatre in Lon-
don’s Westminster borough in 1888, she
was dressed for the occasion. She was
playing Lady Macbeth, and her man-
ner and appearance needed to con-
vey both great beauty and a certain
otherworldliness, perhaps even evil. Her
green dress, shimmering with blue-green
light, perfectly matched the mood. But it
wasn’t a dye that lent that dress (still view-
able at Smallhythe Place in Kent) its eerie,
glittering glamor; it was the wing cases
of a species of glossy, iridescent beetle,
woven by the hundreds into the material.
People have long been fascinated by
the many members of the animal kingdomthat are bright and shiny in this way. Iri-
descence is a visual property in which the
perceived color of an object changes based
on the angle it’s seen from, while glossi-
ness—also called specularity—refers to its
shine. Put another way, while iridescent
surfaces reflect different wavelengths of
light depending on the viewing angle, a
glossy surface reflects all wavelengths at
once, creating a mirror-like effect.
The combination of these properties
give the Buprestidae family of jewel bee-
tles, among other animals, their character-
istic metallic sheen. Amanda Franklin, an
ecologist at the University of Melbourne,
became interested in these beetles hav-
ing previously gotten hooked on study-
ing color and vision through her work on
mantis shrimp, which not only see morecolors than humans do but are sensitive to
multiple types of polarized light. Studying
shrimp’s highly complex sensory systems
ended up being excellent prep work for
studying the comparatively simple mech-
anisms that determine the appearance of
insect wing cases.
The iridescent shine of many beetles is
produced structurally, she explains. Instead
of having specialized pigments that absorb
some wavelengths of light and reflect oth-
ers, which can be metabolically expensive,
it’s the physical features of these insects’ cuti-MORE THAN A LOOK? Scientists have long
puzzled over why some insects, such as this
species of jewel beetle (Sternocera aequisignata),
have glossy surfaces.NOTEBOOK