Role of visual cues and interaction with host odour during the host-finding behaviour of the cabbage moth

The approach and landing responses of female Mamestra brassicae (L.) (Lepid optera: Noctuidae) to visual cues from artificial plant leaves of different shapes and presence/absence of cabbage plant odour were investigated in a laboratory wind tunnel. The leaves were painted with cadmium yellow colour and observed under dim red light. Females showed oriented flight towards pl ant odours but landed significantly more often when the odour was presented with an artificial leaf. In three-choice tests, the shape of the leaf targ ets (circle, square or triangle) did not influence the female response. How ever, the size of the target did influence the insect response: the females preferred landing on square targets with sides of 5 or 10 cm rather than o n the largest target, with sides of 15 cm. The orientation of the target in fluenced the insects' response: females landed significantly more often on the target positioned vertically than horizontally.