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International audience; Disruption experiments were carried out under vineyard conditions and in the laboratory. Males from laboratory cultures were conditioned in an atmosphere permeated with pheromone (E7 Z9-12Ac), marked externally with fluorescent powder, and released in the middle of vine plots. They were then trapped in a series of traps baited with virgin females or dispensers loaded with various amounts of pheromone. Over 10,000 males were released in these experiments between 19 May and 22 July. Electroantennography tests were used for studying olfactory sensitivity in pheromone-permeated air by measuring the EAG responses of male antennae in constant pheromone air-flows. The conclusion is that both sensory adaptation and central nervous system habituation mechanisms acted simultaneously in air laden with pheromone, but they are probably not relevant when concentrations are of the same order of magnitude as those obtained under field conditions in which mating disruption methods are used for controlling the European grape moth.

International audience; S. latifascia and S. descoinsi are closely related species that occur sympatrically over limited areas in French Guiana. We examined allopatric populations, S. latifascia originating from Barbados and S. descoinsi from French Guiana. Studies on nocturnal activity cycles showed temporal partitioning of female calling behavior, male sexual activity, and mating behavior.S. descoinsi were sexually active in the first half of the scotophase whereas S. latifascia were sexually active in the second half. Seven compounds (Z9–14: Ac,Z9,E12–14: Ac,Z11–16: Ac,E9,E12–14: Ac,Z9–14: Ald,Z9,E11–14: Ac andZ11–14: Ac) were identified in females of both S. latifascia and S. descoinsi extracts.Z9–14: Ac was a main pheromone component for the two species. The major difference between the pheromones of S. latifascia and S. descoinsi was the proportion of Z9,E12–14: Ac in the extracts: 7% for S. latifascia and 42% for S. descoinsi. The proportion of Z9,E12–14: Ac relative to the sum of Z9–14: Ac andZ9,E12–14: Ac in individual gland extracts was 4±1% (mean ± standard deviation) for S. latifascia and 44.8±6% for S. descoinsi. Electrophysiological studies showed no major differences between species in the morphology and physiology of the pheromone receptors of males. Receptors were identified for Z9–14: Ac and Z9,E12–14: Ac, but no receptor was found for the other compounds. In the wind tunnel, synthetic blends with Z9–14: Ac and Z9,E12–14: Ac gave the same behavioral responses as conspecific female extracts for the males of the two species. Some cross-attraction was observed with synthetic blends and female extracts. Nethertheless, previous field trapping experiments in French Guiana were species-specific and suggested differences in the attractivity of males. In the laboratory, S. latifascia and S. descoinsi could hybridize in both reciprocal crosses. Female S. descoinsi × male S. latifascia mating rate was significantly lower than for the reciprocal cross, and 26.7% of female S. descoinsi could not separate from male S. latifascia after mating. These copulatory problems may involve genital incompatibilities between males and females. Several barriers against interbreeding between S. latifascia and S. descoinsi seem to combine including differences in nocturnal activity cycles, pheromone differences, and genital barriers. The study of sympatric populations will be necessary to define the role of sex pheromones in the reproductive isolation of S. latifascia and S. descoinsi.

International audience; The noncontingent distribution ofO. nubilalis Hbn. eggs on various corn varieties has allowed their classification as either "favorable" or "nonfavorable" hybrids. This classification is based on a chemical communication system using volatile compounds active at a distance from the insect or active when in contact with the insect as soluble sugar components. Under this hypothesis, gas chromatography is the best way of investigating for the chemical differences between corn silk extracts from the two types of hybrids. A first experiment, using a "desorption-trapping" system on Tenax coupled to a gas chromatograph showed a quantitative difference between two compounds from the two hybrids. A second experiment showed the advantages and disadvantages of this method and allowed the development of two complementary techniques: (1) direct extraction of corn silk with trichlorofluo-romethane and direct injection into a capillary column with an apolar stationary phase using an "on-column" system; and (2) extraction under vacuum of volatile compounds from corn silk and their trapping on Tenax, followed by a second desorption. This allows a direct injection on the same capillary column. The first technique allows identification by mass spectrometry of many alkanes with high molecular weights. The second technique seems to confirm the presence of phenylacetaldehyde. Both techniques show quantitative differences in the composition of corn silk extracts from "favorable" and "nonfavorable" hybrids; however, the biologically active chemicals remain unknown.