Male moths use sex pheromones to find their mating partners. In the moth, Agrotis ipsilon, the behavioral response and the neuron sensitivity within the primary olfactory centre, the antennal lobe (AL), to sex pheromone increase with age and juvenile hormone (JH) biosynthesis. By manipulating the JH level, we previously showed that JH controls this age-dependent neuronal plasticity, and that its effects are slow (within 2 days). We hypothesized that the hormonal effect might be indirect, and one neuromodulator candidate, which might serve as a mediator, is octopamine (OA). Here, we studied the effects of OA and an OA receptor antagonist, mianserin, on behavioral and AL neuron responses of mature and immature males during stimulation with sex pheromone. Our results indicate that, although OA injections enhanced the behavioral pheromone response in mature males, OA had no significant effect on behavior in immature males. However, mianserin injections decreased the behavioral response in mature males. AL neuron sensitivity increased after OA treatment in immature males, and decreased after mianserin treatment in mature males. Determination of OA levels in ALs of immature and mature males did not reveal any difference. To study the possible interactive effects of JH and OA, the behavioral pheromone response was analyzed in JH-deprived mature males injected with OA, and in immature males injected with fenoxycarb, a JH agonist, and mianserin. Results show that both JH and OA are necessary to elicit a behavioral response of A. ipsilon males to sex pheromone.

In the European grapevine moth, Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae), it has recently been shown that volatiles emitted from the main host plant, grapevine, are attractive to adult females. Here, using wind tunnel experiments, we tested the attractiveness of various grapevine, Vitis vinifera L. (Vitaceae), plant parts at different phenological stages, including ripe berries infested with the pathogenic fungus Botrytis cinerea (Persoon: Fries) (Sclerotiniaceae) to laboratory‐reared virgin and mated male and female moths. We also tested the attractiveness of the non‐host plant, tansy [Tanacetum vulgare (L.) (Asteraceae)], as flowers and flower volatiles were previously shown to be attractive to L. botrana females in the field. Mated female moths were the only adults to exhibit upwind orientation to grape plant parts in the flight tunnel. The most attractive parts of the grapevine plants were leaves, flower buds, and ripe berries. No attraction was observed to flowers. This corresponds to the phenological stages available when females of the 2–3 generations during a year are present in the field. No attraction was observed to leaves and flowers of tansy.

Spatiotemporal odour coding is thought to be linked closely with the specific glomerular anatomy of the primary olfactory centre. In most insects the number of the glomeruli within the antennal lobe is limited to fewer than 100, allowing their individual identification. In the grapevine moth, Lobesia botrana, a map of the antennal lobe glomeruli was reconstructed three-dimensionally, by comparing three different brains in males and females. The map of the antennal lobe of females served then as a basis to identify glomeruli containing dendritic arborisations of 14 physiologically characterised projection neurons. Projection neurons responding to the same plant compound did not always arborise in the same glomerulus and some neurons arborising in the same glomerulus responded to different compounds. Different zones of target glomeruli were, however, identified when pooling all neurons responding to one of two different compounds respectively (alpha-farnesene and nonatriene). All identified glomeruli of specifically responding projection neurons were situated close to the anterior surface of the antennal lobe. One broadly responding projection neuron arborised in a more posteriorly situated glomerulus. A local interneuron responding to only one compound was arborising densely in a neighbouring glomerulus and had sparse branches in all other glomeruli. These results are discussed with respect to plant odour processing and structure-function relations in antennal lobe neurons. The 3D AL atlas will, in the future, also be used to obtain a better understanding of coding mechanisms of grapevine odours in this pest insect.