Phototactic behaviour of the parasitoid Encarsia formosa (Hymenoptera: Aphelinidae)

We investigated the spectral sensitivity and response to light intensity of Encarsia formosa (Hymenoptera: Aphelinidae), which is a key natural enemy of the greenhouse whitefly, Trialeurodes vaporariorum, and the tobacco whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae). To do so, we used 15 monochromatic lights (emitting various specific wavelengths from 340 to 649 nm) and white light. E. formosa adults, which are diurnal insects, showed a positive phototaxis to a broad spectrum of light, with peaks of sensitivity at 414, 340, 450, and 504 nm. These results show that this parasitoid is generally more sensitive to short wavelength lights than long wavelength lights across all spectral ranges tested. Furthermore, E. formosa adults showed an increased phototactic response at low intensities and a decreased response at high intensities, for both ultraviolet light and violet light. Thus, E. formosa showed both colour and intensity preferences. This experiment provides a scientific basis for the development of colour traps for insect pest management and improves understanding of the ecological significance of colour vision by E. formosa.