Field Observations on Attractiveness of Selected Blooming Plants to Noctuid Moths and Electroantennogram Responses of Black Cutworm (Lepidoptera: Noctuidae) Moths to Flower Volatiles

SUMMARYIn the moth, Agrotis ipsilon, newly mated males cease to be attracted to the female-produced sex pheromone, preventing them from re-mating until the next night, by which time they would have refilled their reproductive glands for a potential new ejaculate. The behavioural plasticity is accompanied by a decrease in neuron sensitivity within the primary olfactory centre, the antennal lobe (AL). However, it was not clear whether the lack of the sexually guided behaviour results from the absence of sex pheromone detection in the ALs, or if they ignore it in spite of detection, or if the sex pheromone itself inhibits attraction behaviour after mating. To test these hypotheses, we performed behavioural tests and intracellular recordings of AL neurons to non-pheromonal odours (flower volatiles), different doses of sex pheromone and their mixtures in virgin and newly mated males. Our results show that, although the behavioural and AL neuron responses to flower volatiles alone were similar between virgin and mated males, the behavioural response of mated males to flower odours was inhibited by adding pheromone doses above the detection threshold of central neurons. Moreover, we show that the sex pheromone becomes inhibitory by differential central processing: below a specific threshold, it is not detected within the AL; above this threshold, it becomes inhibitory, preventing newly mated males from responding even to plant odours. Mated male moths have thus evolved a strategy based on transient odour-selective central processing, which allows them to avoid the risk-taking, energy-consuming search for females and delay re-mating until the next night for a potential new ejaculate.

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 98%

Switching attraction to inhibition: mating-induced reversed role of sex pheromone in an insect

Barrozo¹,

Gadenne²,

Anton³

2010

“…The males show the highest attraction to a mixture of the three components at a ratio of 4:1:4 (Causse et al, 1988). Heptanal, a component of linden flower extract, proved to be very attractive on the behavioural level and to evoke strong responses in electroantennographic and intracellular recordings in the AL (Wynne et al, 1991;Zhu et al, 1993;Greiner et al, 2002;Barrozo et al, 2011). Antennae were stimulated with the threecomponent pheromone blend, heptanal and a mixture of heptanal and the pheromone blend.…”

Section: Olfactory Stimulationmentioning

confidence: 99%

“…As multiple odours coincide in a natural environment, it may be advantageous for A. ipsilon males to respond to a mixture of pheromone and heptanal, a component emitted by linden flowers (Zhu et al, 1993), because this food source might represent an additional cue indicating the presence of females. Behavioural pheromone responses of A. ipsilon males in a wind tunnel were improved when heptanal was added, and this synergistic effect was particularly evident at the dose we used in the present study (Barrozo et al, 2010).…”

Section: Behavioural Relevance Of Mixture Coding Properties In the Almentioning

confidence: 99%

Plant odour stimuli reshape pheromonal representation in neurons of the antennal lobe macroglomerular complex of a male moth

Chaffiol¹,

Kropf²,

Barrozo³

et al. 2012

SUMMARYMale moths are confronted with complex odour mixtures in a natural environment when flying towards a female-emitted sex pheromone source. Whereas synergistic effects of sex pheromones and plant odours have been observed at the behavioural level, most investigations at the peripheral level have shown an inhibition of pheromone responses by plant volatiles, suggesting a potential role of the central nervous system in reshaping the peripheral information. We thus investigated the interactions between sex pheromone and a behaviourally active plant volatile, heptanal, and their effects on responses of neurons in the pheromone-processing centre of the antennal lobe, the macroglomerular complex, in the moth Agrotis ipsilon. Our results show that most of these pheromone-sensitive neurons responded to the plant odour. Most neurons responded to the pheromone with a multiphasic pattern and were anatomically identified as projection neurons. They responded either with excitation or pure inhibition to heptanal, and the response to the mixture pheromone + heptanal was generally weaker than to the pheromone alone, showing a suppressive effect of heptanal. However, these neurons responded with a better resolution to pulsed stimuli. The other neurons with either purely excitatory or inhibitory responses to all three stimuli did not exhibit significant differences in responses between stimuli. Although the suppression of the pheromone responses in AL neurons by the plant odour is counterintuitive at first glance, the observed better resolution of pulsed stimuli is probably more important than high sensitivity to the localization of a calling female. Supplementary material available online at

“…Nectar-feeding moths are attracted to the odours of their floral hosts (Heath et al, 1992;Zhu et al, 1993). These odours are a complex blend of individual volatile components, each with a different biosynthetic route to their production and a potentially different effect on insect behaviour (Pichersky and Gershenzon, 2002).…”

mentioning

confidence: 99%

Learning, odour preference and flower foraging in moths

Cunningham

Moore

Zalucki

et al. 2004

147

100

Floral volatiles play a major role in plant-insect communication. We examined the influence of two volatiles, phenylacetaldehyde and α-pinene, on the innate and learnt foraging behaviour of the moth Helicoverpa armigera. In dual-choice wind tunnel tests, adult moths flew upwind towards both volatiles, with a preference for phenylacetaldehyde. When exposure to either of these volatiles was paired with a feeding stimulus (sucrose), all moths preferred the learnt odour in the preference test. This change in preference was not seen when moths were exposed to the odour without a feeding stimulus. The learnt preference for the odour was reduced when moths were left unfed for 24·h before the preference test.We tested whether moths could discriminate between flowers that differed in a single volatile component. Moths were trained to feed on flowers that were odour-enhanced using either phenylacetaldehyde or α-pinene. Choice tests were then carried out in an outdoor flight cage, using flowers enhanced with either volatile. Moths showed a significant preference for the flower type on which they were trained. Moths that were conditioned on flowers that were not odour-enhanced showed no preference for either of the odour-enhanced flower types. The results imply that moths may be discriminating among odour profiles of individual flowers from the same species. We discuss this behaviour within the context of nectar foraging in moths and odour signalling by flowering plants.