Odour perception in the codling moth Cydia pomonella L.

The codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae) is a renowned pest in apple, pear and walnut orchards, and its activities are in large guided by volatile odours as sensory cues. This thesis spans over a large part of the olfactory chain of events in the codling moth, from brain to behaviour. The main emphasis was placed on the detection of plant odours, and some of the works presented are novel to codling moth research. The volatiles emitted by host-plant species were analysed, revealing variations in the odour profiles both between species of host plants and at different phenological stages of a host plant, which indicates that females are flexible in their behavioural response to host odours. A first step was taken to map the antennal olfactory receptor neurons and their specificity, where several behaviourally active compounds were found to be detected by neurons housed in sensilla auricillica, one of the morphological types of sensilla found on the antenna of the moth. In a study of the antennal lobe, the primary integration centre for odour processing in the insect brain, we describe the three dimensional structure of the array of olfactory glomeruli of both sexes. Behavioural experiments show that both males and females are attracted to plant odours, and that host recognition in codling moths are encoded not by single compounds but by a blend of volatiles. Taken together, the results presented in this thesis provide new insights into moth olfaction and odour-dependent behaviour in general, and into that of the codling moth in particular.