Visual behaviour of the greenhouse whitefly, Trialeurodes vaporariorum

. The behaviour of Trialeurodes vaporariorum (Westwood) (Homoptera, Aleyrodidae) in violet and green light (400 and 550 nm) was examined using several responses. Under 400 nm the whiteflies took‐off more readily and walked faster than under 500 nm. In flight, they oriented towards 400 nm when simultaneously illuminated with equal quanta of 550 and 400 nm light. The ecological significance of this behaviour is discussed, and it is concluded that in nature flying adults would orient towards the sky (i.e. c. 400 nm) but would tend to land on a green plant because plants reflect maximally at 550 nm. Once landed on a suitable food‐plant the position on that plant where the insect finally feeds and reproduces is probably also determined by visual stimuli, since whiteflies will walk to the shaded side of a leaf regardless of whether that is below or above.