Phototactic Action Spectrum for Whitefly and the Question of Colour Vision

The peak of phototactic response ofTrialeurodes(Asterochitori)vaporariorum(Westw.) to equal numbers of quanta of monochromatic light in the range 475–625 mμ occurred at 540–550 mμ. and a hump of "red" sensitivity occurred near 600 mμ. This coincided with the transmission spectrum of host leaves. The response to light intensity was hyperbolic but it was linear within the variance in the range used for the action spectrum. Corrections were made for decreasing sensitivity during experiments. The absorption spectrum of a pigmented eye-preparation included a shoulder at the wavelength that caused maximal phototaxy. Work on greenhouse light traps is recommended. Preliminary colorimetric data did not support a capacity for colour vision.