Photovoltaic effects in the Oriental hornet, Vespa orientalis

Photoelectric properties of the Oriental hornet ( Vespa orientalis) cuticle and the pupal silk cocoon were studied. Exposure of a part of the cuticle to light caused a sharp increase in voltage, when measured between the illuminated and the dark part of the cuticle. The direction of this voltage was reversed if the other part of the cuticle was illuminated. This voltage was found to be linearly dependent on the intensity of the incident light for relatively low light intensities of a few mW/cm 2. However, this light-induced voltage was much higher if the light beam was directed at the back part of the cuticle strip than in the case where the front part of the cuticle strip was illuminated by the same light beam. The spectral dependence of this effect was also investigated and the maximum of the relative quantum efficiency was found in the spectral range of 360–380 nm. It appears that the cuticle might act as a biological solar cell. The dependence of photo current on the exposure time to light, as well as on environmental conditions, such as temperature and relative humidity was investigated in the pupal silk cocoon. Our results indicate that the cuticle as well as the cocoon act as convertors of light to electrial energy. At present we do not know the absolute efficiency of this conversion process, nor the biological applications of this effect.