Solar Energy Powered Oriental Hornets

BBC - Earth News - Oriental hornets powered by 'solar energy'

The Oriental hornet has a unique ability to harvest solar energy, scientists have discovered.

The large wasp species has a special structure in its abdomen that traps the sun's rays, and a special pigment that harvests the energy they contain.

The discovery helps explain why these hornets have a large yellow stripe across their body and why they become more active as the day gets hotter.

It also changes our understanding of how insect metabolism can work.

Marian Plotkin of Tel Aviv University and colleagues used advanced microscopes to examine a hornet's exoskeleton, or cuticle. Most of the cuticle is brown, but a few sections are yellow. These colours mark the hornet as a venomous insect, and therefore best avoided by potential predators, but the pigments are also involved in mopping up solar energy.

Both the brown and yellow cuticles are made up of many layers laid on top of each other, around 30 in the brown and 15 in the yellow. The brown areas contain melanin, a pigment also found in human skin, while the yellow areas contain xanthopterin.

Plotkin found that the brown cuticle is covered with grooves, while the yellow cuticle is covered with oval-shaped lumps. Both absorbed 99 per cent of the visible light falling on them.

What's more, the grooves on the brown cuticle are fairly regularly spaced, Plotkin found. As a result, the cuticle surface mimics a series of slits, which act as a diffraction grating, trapping yet more light inside the cuticle layers.

The team also built a solar cell that successfully used xanthopterin to harvest light.

Findings from the AFM study of the brown and yellow epicuticle (cuticle surface). a 3D image of the brown cuticle, showing the grating structure. b The profile structure of the grating on the brown cuticle. The grating-like formation has a height of about 160 nm and a period of about 500 nm. c 3D image of the yellow cuticle showing the interlocking pattern of oval-shaped structures. Every oval structure harbors at least one “pinhole” depression. d The profile structure of the grating on the yellow cuticle

Volume 97, Number 12, 1067-1076, DOI: 10.1007/s00114-010-0728-1

Solar energy harvesting in the epicuticle of the oriental hornet (Vespa orientalis)