Interviews
Jewel Beetle with complex structures to create unique colors
30 Jul '09
5 min read
While the structures are determined genetically, their final form depends on the living conditions the beetle experiences during its growth and development, Srinivasarao noted.
The fact that these jeweled beetles reflect circular polarization was identified in the early 1900s by a Nobel Prize-winning physicist, A.A. Michelson, who hypothesized that the circular polarization might result from a “screw structure” within the insect's cuticle, but he did not elaborate on it further. The solidified structures produced from a cholesteric liquid crystal and its defects on the beetle's shell reflect bright green light with a wavelength of 530 nanometers mixed with yellow light in a wavelength of 580 nanometers.
“The most dramatic way to get saturated color is through what this beetle does with the circularly-polarized light,” Srinivasarao said. “The reflection is very metallic and angle-dependent, and this is due to the helical pitch of the cholesteric liquid crystal.”
Sunlight normally contains light in equal quantities with a left circular polarization and a right circular polarization. The jewel beetle's exoskeleton, however, reflects only light with a left circular polarization. Only a few members of the scarab family of beetles reflect both polarizations.
How the beetles benefit from the specific color and polarization isn't known for sure, but scientists speculate that the optical properties may confuse predators, causing them to misjudge the location of the insects – or suggest that they may not be good to eat. The colors may also help the insects find mates.
In future research, Srinivasarao hopes to study other insects that use complex structures to create unique colors. He believes that scientists still have a lot to learn by studying the optical structures of beetles and other insects.
“We are just now starting to catch up with what these beetles have been doing for many, many years,” he said. “There are hundreds of thousand of species, and the way they generate color is just stunning – especially since it is all done with water-based systems, mostly based on the biopolymer chitin. This is self-assembly at several levels, and we need to learn a lot more to duplicate what these insects do.”
The fact that these jeweled beetles reflect circular polarization was identified in the early 1900s by a Nobel Prize-winning physicist, A.A. Michelson, who hypothesized that the circular polarization might result from a “screw structure” within the insect's cuticle, but he did not elaborate on it further. The solidified structures produced from a cholesteric liquid crystal and its defects on the beetle's shell reflect bright green light with a wavelength of 530 nanometers mixed with yellow light in a wavelength of 580 nanometers.
“The most dramatic way to get saturated color is through what this beetle does with the circularly-polarized light,” Srinivasarao said. “The reflection is very metallic and angle-dependent, and this is due to the helical pitch of the cholesteric liquid crystal.”
Sunlight normally contains light in equal quantities with a left circular polarization and a right circular polarization. The jewel beetle's exoskeleton, however, reflects only light with a left circular polarization. Only a few members of the scarab family of beetles reflect both polarizations.
How the beetles benefit from the specific color and polarization isn't known for sure, but scientists speculate that the optical properties may confuse predators, causing them to misjudge the location of the insects – or suggest that they may not be good to eat. The colors may also help the insects find mates.
In future research, Srinivasarao hopes to study other insects that use complex structures to create unique colors. He believes that scientists still have a lot to learn by studying the optical structures of beetles and other insects.
“We are just now starting to catch up with what these beetles have been doing for many, many years,” he said. “There are hundreds of thousand of species, and the way they generate color is just stunning – especially since it is all done with water-based systems, mostly based on the biopolymer chitin. This is self-assembly at several levels, and we need to learn a lot more to duplicate what these insects do.”
Georgia Institute of Technology
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