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See detailHarmonia axyridis population study in agroecosystems
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Durieux, Delphine ULg et al

Poster (2014, October)

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native ... [more ▼]

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native range in Central and Eastern Asia to large parts of North and South America, Europe, and Africa. The decline of native species is linked to the spread and the aggressive behaviour of H. axyridis. From 2009, we evaluated the population densities of aphids predator and predator diversities, with a special focus on H. axyridis in agroecosystems of Wallonia (South of Belgium). First, field crops preferences of H. axyridis were determined. Later, changes linked to aphid’s predator populations over time were evaluated. Finally, H. axyridis population changes between two crop farming methods were also evaluated. Samplings performed in agroecosystems highlighted that the community of aphid's predator is composed of few dominant species: three coccinellids (Coccinella septempunctata L., P. quatuordecimpunctata L., and H. axyridis), one syrphid (Episyrphus balteatus De Geer), and one chrysopid (Chrysoperla carnea Stephens). We demonstrated that H. axyridis do not invade all crops at the same rate, maize and broad bean being more infested than wheat and potato at both larval and adult stages. Moreover, H. axyridis populations in maize have strongly increased from 2009 to 2011. Finally, we showed that organic farming do not contribute to increase the abundance of H. axyridis but leads to increase the total abundance of aphid’s natural enemies. [less ▲]

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See detailStudy of sex ratio and morphotypes of the Multicoloured Asian Ladybird, Harmonia axyridis Pallas in Belgian maize
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Barsics, Fanny ULg et al

Poster (2014, October)

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian ... [more ▼]

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian Ladybird, which is considered as an invasive species in Europe since its introduction in the 80’s. Harmonia axyridis has four major morphotypes: 2 melanic forms, conspicua and spectabilis; and 2 non-melanic, succinea and axyridis. In Belgium, only the three first are observed. Literature reports variations in morphotype frequencies, across native and introduced strains. These variations seem to be linked to climate (geographical and seasonal variation), with non-melanic forms being the most abundant in hot and arid climate. This study focused on the variation of morphotype abundance in H. axyridis according to season, field and gender. Adult ladybirds were caught from mid-July to mid-October 2012 into 5 maize fields. The proportions of observed morphotypes were compared according to the sampling season. The abundance of morphotypes was not significantly different through the fields; the observed ratios were 81.6%, 15% and 3.4% for succinea, spectabilis and conspicua respectively. Succinea was the most observed morphotype (χ2=755.8; P<0.001). The total number of collected males and females was the same with ratios of 48.2% and 51.8%: (χ2=0.93; P=0.33). The sex ratio was also not significantly different for each morphotype. There was no evolution of melanic and non-melanic form ratio according to the season, with 25.6% of melanic form in summer and 20.6% in autumn (χ2=1.22; P=0.27). Our results seem to show that morphotype adaptation according to the climate is not observed for Belgian ladybirds. [less ▲]

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See detailUne phéromone sexuelle chez la coccinelle asiatique, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

Conference (2014, October)

A ce jour, aucune phéromone sexuelle n’a pu être mise en évidence chez les Coccinellidae. Cependant, diverses études suggèrent que de telles molécules sont impliquées dans la communication sexuelle chez ... [more ▼]

A ce jour, aucune phéromone sexuelle n’a pu être mise en évidence chez les Coccinellidae. Cependant, diverses études suggèrent que de telles molécules sont impliquées dans la communication sexuelle chez les coccinelles. Afin de vérifier cette hypothèse, nous avons collecté les composés organiques volatils émis par la coccinelle asiatique, Harmonia axyridis (Pallas), en présence ou en absence de pucerons. En présence de pucerons, les femelles vierges présentent un « comportement d’appel » qui est notamment associé à l’émission d’une phéromone sexuelle volatile chez plusieurs espèces de Coléoptères. D’autre part, des tests éthologiques ont démontré que les femelles émettent des composés volatils qui attirent les mâles à distance. Enfin, les prélèvements ont été analysés par chromatographie en phase gazeuse couplée à la spectrométrie de masse. Les analyses ont mis en évidence cinq composés volatils spécifiques provenant des femelles, aucun d’entre eux n’étant émis pas les mâles. L’identification a révélé la présence de (–)-β-caryophyllène, de β-élémène, de méthyl-eugénol, d’α-humulène et d’α-bulnésène, exclusivement produits par les femelles nourries de pucerons et dont les quantités respectives augmentent progressivement au cours de la période de prélèvement. Les résultats confirment donc que les femelles H. axyridis produisent une phéromone sexuelle volatile. Ceux-ci devraient permettre de promouvoir le développement de méthodes de gestion plus efficaces afin de manipuler les mouvements de cette coccinelle invasive et de réduire les impacts négatifs qu’elle occasionne sur la biodiversité. [less ▲]

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See detailEvolution des populations de coccinelles indigènes et de l’espèce exotique, Harmonia axyridis Pallas, en Wallonie et en Région de Bruxelles-Capitale
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Durieux, Delphine ULg et al

Conference (2014, October)

Un inventaire des Coccinellidae provenant de la collection de l’unité d’Entomologie fonctionnelle et évolutive (ULg - Gembloux Agro-Bio Tech) a été réalisé sur une période s’étendant de 2001 à 2009. Cette ... [more ▼]

Un inventaire des Coccinellidae provenant de la collection de l’unité d’Entomologie fonctionnelle et évolutive (ULg - Gembloux Agro-Bio Tech) a été réalisé sur une période s’étendant de 2001 à 2009. Cette collection est essentiellement constituée de récoltes fournies par les étudiants de première Bachelier de Gembloux Agro-Bio Tech. A travers ce recensement, nous avons étudié l’évolution des espèces récoltées au sein de cette famille, en termes d’effectif relatif et de richesse spécifique. Notre étude s’est focalisée sur les données issues de Wallonie et de la Région de Bruxelles-Capitale, car trop peu de collectes ont été réalisées en Flandre. Parmi les individus identifiés, 27 espèces ont été observées, dont 21 appartiennent à la sous-famille des Coccinellinae, 2 à celle des Epilachninae et 4 à celle des Chilocorinae. La plupart des espèces sont communes à la Belgique. Cependant, Harmonia axyridis (Pallas 1773), espèce originaire du sud-est de l’Asie, a été introduite sur le territoire belge en 1997. Cette coccinelle exotique a fait son apparition dans les collectes de 2002 et son effectif ne cesse d’augmenter au fil des années prospectées. En parallèle à cette augmentation, une diminution de la richesse spécifique, ainsi que de l’effectif relatif d’Adalia bipunctata (L. 1758), de Propylea quatuordecimpunctata (L. 1758) et de Psyllobora vigintiduopunctata (L. 1758), est observée. [less ▲]

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See detailIs Contact Between Conspecifics Involved in the Cohesion of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) Aggregations?
Durieux, Delphine ULg; Fassotte, Bérénice ULg; Fischer, Christophe ULg et al

in Journal of Insect Behavior (2014), 27(1), 1-13

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), exhibits a gregarious behavior during unfavorable winter conditions. Although this behavior is currently described as a phenomenon occurring ... [more ▼]

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), exhibits a gregarious behavior during unfavorable winter conditions. Although this behavior is currently described as a phenomenon occurring only during winter, aggregations can also be observed outside overwintering conditions. However, the substrate markings previously highlighted as being involved in the wintry aggregation of this exotic species do not seem to be used by non-overwintering individuals to aggregate. This fact suggests then that other cues are responsible for the induction of this behavior. In this work, we have tested the hypothesis that direct contact between non-overwintering individuals stimulates the establishment of clusters. Binary choice experiments highlighted the involvement of elytral cuticular compounds in this phenomenon. Chromatographic analyses showed that the active extracts contained mainly hydrocarbons, including saturated, mono-unsaturated, and di-unsaturated homologues. Physical contact also seems to be involved in the non-overwintering aggregative behavior of H. axyridis, but to a lesser extent than these natural compounds. These findings could eventually be used to develop new control methods of these pest populations and so, reduce the adverse impacts it causes on biodiversity. [less ▲]

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See detailIs conspecific substrate marking a long-term external memory of previously colonized overwintering sites in Harmonia axyridis?
Durieux, Delphine ULg; Fassotte, Bérénice ULg; Vanderplanck, Maryse et al

in Journal of Applied Entomology (2014), 138(5), 338-345

The multicoloured Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during winters to survive the cold. This beetle uses chemical cues coming from congeners to select an ... [more ▼]

The multicoloured Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during winters to survive the cold. This beetle uses chemical cues coming from congeners to select an overwintering site. Recent research has shown that they preferentially gather at places where conspecifics previously laid a substrate marking made up of saturated and unsaturated hydrocarbons. Some authors have reported that H. axyridis colonizes the same overwintering sites from 1 year to another. Herein, the hypothesis that this substrate marking is used by H. axyridis to settle in the same aggregation sites from one winter to another was tested. To this aim, the temporal modification in the chemical profile of the hydrocarbon marking was studied by performing chromatographic analyses. After 1 year, the overall profile was modified qualitatively and quantitatively: the unsaturated hydrocarbons were no longer detected while some saturated hydrocarbons were still present in large quantities. In a behavioural assay conducted in the laboratory, the 12-month-old marking did not induce the aggregation of H. axyridis. This result indicates that the chemical markings left by conspecifics during a previous aggregation period in an overwintering site are not sufficient to induce the gathering of the newly arriving individuals. [less ▲]

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See detailFive Years of aphidophagous species sampling in belgian corn
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Durieux, Delphine ULg et al

Poster (2014, May 20)

The community of aphidophagous species present in agroecosystems is disturbed since the introduction of an exotic species the Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera ... [more ▼]

The community of aphidophagous species present in agroecosystems is disturbed since the introduction of an exotic species the Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae). In this intensive agricultural area, five aphids predator species are commonly observed: three coccinellids H. axyridis, Coccinella septempunctata, Propylea quatuordecimpunctata, one hoverfly Episyrphus balteatus, and one lacewing Chrysoperla carnea. This study focuses on the occurrence of the five most abundant aphid predators and their seasonal abundance in corn. The abundance of adults and larvae of these species was evaluated over a five-year period, from 2009 to 2013. The sampling method consisted in the counting of aphids and all developmental stages of aphidophages present in quadrats of 1m² from April to November. Densities of aphid predators changed during five years studies. Since 2011, H. axyridis was the most abundant aphids predators in corn. H. axyridis numbers were found to increase over the first four inventoried year, reaching in 2012 86% for adult stage (119,7±7,8 adults/100m2) and 76% for larvae stages (242,8±14,2 larvae/100m2) of the aphid predators, while in 2009 these ratios were 14% and 23% respectively. For C. septempunctata and P. quatuordecimpunctata the population densities decrease at the end of the five years period. Population densities of C. carnea and E. balteatus were variable during the sampling period but increased in 2013. Phenology of the five studied species presents similar curves following the aphid abundance. The most abundant observed aphids were metopolophium dirhodum, rhopalosiphum padi, rhopalosiphum maidis, sitobion avenae and sitobion fragariae. H. axyridis starts reproducing after the peak in aphid population, suggesting that H. axyridis is able to complete its development by feeding on alternative prey such as larvae and pupae of conspecific and heterospecific. H. axyridis is a bivoltine species but the second generation was stop by the corn harvesting. [less ▲]

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See detailConservatoire entomologique de Gembloux Agro-Bio Tech: les coccinelles de Wallonie et de Bruxelles de 2001 à 2009
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Durieux, Delphine ULg et al

Poster (2014, April 02)

Un inventaire des Coccinellidae présents au sein de la collection de l’unité d’Entomologie fonctionnelle et évolutive (ULg - Gembloux Agro-Bio Tech) a été réalisé sur la période s’étendant de 2001 à 2009 ... [more ▼]

Un inventaire des Coccinellidae présents au sein de la collection de l’unité d’Entomologie fonctionnelle et évolutive (ULg - Gembloux Agro-Bio Tech) a été réalisé sur la période s’étendant de 2001 à 2009. Cette collection est essentiellement constituée par les récoltes des étudiants de première Bachelier de Gembloux Agro-Bio Tech. A travers ce recensement, nous avons étudié l’évolution des espèces récoltées au sein de cette famille en termes d’effectif relatif et de richesse spécifique. Notre étude s’est focalisée sur les données issues de Wallonie et de la Région de Bruxelles-Capitale, trop peu de collectes ayant été réalisées en Flandre. Parmi les individus identifiés, 27 espèces ont été observées, dont 21 appartiennent à la sous-famille des Coccinellinae, 2 à celle des Epilachninae et 4 à celle des Chilocorinae. La plupart des espèces sont communes à la Belgique. Cependant, Harmonia axyridis (Pallas 1773), espèce originaire du sud-est de l’Asie, a été introduite sur le territoire belge en 1997. Cette coccinelle exotique fait son apparition dans les récoltes de 2002 et son effectif ne cesse d’augmenter au fil des années prospectées. En parallèle à cette augmentation, une diminution de la richesse spécifique, ainsi que de l’effectif relatif d’Adalia bipunctata (L. 1758), de Propylea quatuordecimpunctata (L. 1758) et de Psyllobora vigintiduopunctata (L. 1758), est observée. [less ▲]

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See detailStudy of sex ratio and morphotypes of the Multicoloured Asian Ladybird, Harmonia axyridis Pallas in Belgian corn
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Barsics, Fanny ULg et al

Poster (2014, April 02)

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian ... [more ▼]

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian Ladybird, which is considered as an invasive species in Europe since its introduction in the 80’s. Harmonia axyridis has four major morphotypes: 2 melanic forms, conspicua and spectabilis; and 2 non-melanic, succinea and axyridis. In Belgium, only the three first are observed. Literature reports variations in morphotype frequencies, across native and introduced strains. These variations seem to be linked to climate (geographical and seasonal variation), with non-melanic forms being the most abundant in hot and arid climate. This study focused on the variation of morphotype abundance in H. axyridis according to season, field and gender. Adult ladybirds were caught from mid-July to mid-October 2012 into 5 corn fields. The proportions of observed morphotypes were compared according to the sampling season. The abundance of morphotypes was not significantly different through the fields; the observed ratios were 81.6%, 15% and 3.4% for succinea, spectabilis and conspicua respectively. Succinea was the most observed morphotype (χ2=755.8; P<0.001). The total number of collected males and females was the same with ratios of 48.2% and 51.8%: (χ2=0.93; P=0.33). The sex ratio was also not significantly different for each morphotype. There was no evolution of melanic and non-melanic form ratio according to the season, with 25.6% of melanic form in summer and 20.6% in autumn (χ2=1.22; P=0.27). Our results seem to show that morphotype adaptation according to the climate is not observed for Belgian ladybirds. We discuss these results according to all environmental data available. [less ▲]

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See detailFirst evidence of a volatile sex pheromone in the invasive Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

Conference (2014, April 02)

Data about sex pheromones, or any semiochemicals that play a role in Coccinellid mating, remain limited. Since years, various studies and behavioral observations have hypothesized that such molecules are ... [more ▼]

Data about sex pheromones, or any semiochemicals that play a role in Coccinellid mating, remain limited. Since years, various studies and behavioral observations have hypothesized that such molecules are involved in sexual communication of ladybeetles. In this study, we collected volatile organic compounds released by virgin females of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), which were either allowed or not allowed to feed on aphids. In the presence of aphids, virgin females exhibited “calling behavior”, which has been associated with the emission of a sex pheromone in several Coleoptera species. Bioassays showed that these females released a blend of volatile compounds that is involved in the attraction of males. Gas Chromatography-Mass Spectrometry analyses highlighted specific volatile cues emanating from females, whereas males did not produce these compounds. Five components were identified: (–)-β-caryophyllene, β elemene, methyl-eugenol, α humulene, and α bulnesene. All compounds were produced after virgin females were fed aphids, and their quantity increased across the experimental period. The results confirm that female H. axyridis produce a volatile sex pheromone. Therefore, this study provides important biological information that could promote the development of efficient pest control management methods to manipulate the movements of this invasive ladybeetle, and to reduce its negative impacts on biodiversity. [less ▲]

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See detailA pheromone-based formulation against phytophagous pests
Fassotte, Bérénice ULg; Vandereycken, Axel ULg; Heuskin, Stéphanie ULg et al

Poster (2014, April 02)

Innovative integrated pest management methods are needed to overcome market withdrawal of synthetic pesticides. Therefore, the identification of environment-friendly bio-products carrying direct or ... [more ▼]

Innovative integrated pest management methods are needed to overcome market withdrawal of synthetic pesticides. Therefore, the identification of environment-friendly bio-products carrying direct or indirect biocide activity is one promising alternative option. Our researches focus on the identification of appropriate formulations releasing volatile organic compounds that are attractive for natural enemies of insect pests. However, the elaboration of slow-release devices that ensure stable and controlled release of active volatile compounds is quite challenging. Here, we developed a formulation based on E-β-farnesene and (–)-β-caryophyllene, these two semiochemicals having strong attractive potential on aphid natural enemies including ladybeetles and hoverflies. Both compounds were encapsulated together in alginate gel beads. The blend efficiency is currently being evaluated through laboratory and field assays. [less ▲]

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See detailA volatile sex pheromone in the invasive ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

in Communications in Agricultural and Applied Biological Sciences (2014), 79(1), 79-81

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See detailFirst Evidence of a Volatile Sex Pheromone in Harmonia axyridis (Pallas)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

Poster (2013, October)

Until now, no volatile sex pheromone has been highlighted in Coccinellidae but various studies have suggested the existence of such molecules. In the present work, we have sampled volatile organic ... [more ▼]

Until now, no volatile sex pheromone has been highlighted in Coccinellidae but various studies have suggested the existence of such molecules. In the present work, we have sampled volatile organic compounds released in the headspace of virgin females in the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), that were either allowed or not to feed on pea aphids (Acyrthosiphon pisum Harris). When fed on aphids, virgin females showed a stereotypical “calling behavior”, commonly associated with the emission of a sex pheromone in several Coleoptera species. Behavioral assays conducted with calling females in a four-arm olfactometer demonstrated that the blend of released volatile compounds was attractive at a distance for males, but not for other females. The headspace of virgin females that were not previously fed with aphids was not attractive for either sex. GC-MS analyses revealed the presence of five compounds in the volatile blend: (–)-β-caryophyllene, β-elemene, methyl-eugenol, α-humulene and α-bulnesene. Subsequently, we have collected and quantified the constituents from the blend over a period of 9 days after exposure to aphids. All five compounds were produced exclusively after feeding virgin females with aphids, and their quantity significantly increased during the whole period of collection. (–)-β-caryophyllene was found to be the major constituent, representing between 80 and 86 % of the total blend. All these results could promote the development of more specific and efficient management methods to manipulate the movements of this invasive ladybeetle and to reduce its negative impacts on biodiversity. [less ▲]

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See detailThe Multicoloured Asian Ladybird, invasive or not in agroecosystems ?
Vandereycken, Axel ULg; Durieux, Delphine ULg; Fassotte, Bérénice ULg et al

Poster (2013, September 10)

The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. Its occurrence in agroecosystems remains poorly ... [more ▼]

The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. Its occurrence in agroecosystems remains poorly documented. This study focuses on the occurrence of this exotic species and its seasonal abundance in various field crops. The abundance of adults and larvae of H. axyridis was evaluated over a four-year period, from 2009 to 2012, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. A total of 28 aphid predator species were observed including 14 coccinellid species, 13 hoverfly species and one lacewing species. H. axyridis is present and reproduces in all of the four crops studied, with the largest numbers recorded in corn and broad bean crops. In corn, H. axyridis numbers were found to increase over the four inventoried year, reaching 86% of the aphid predators in 2012, while it represented only 15% in 2009. H. axyridis was not always recorded where aphids were abundant, e.g. aphids were abundant on wheat where no H. axyridis were recorded. H. axyridis starts reproducing after the peak in aphid population, suggesting that H. axyridis is able to complete its development by feeding on alternative prey such as larvae and pupae of the same and other species of ladybird and other aphidophagous species. H. axyridis is often considered to be bivoltine but it only completes one generation per year in field crops. The second generation generally develops late in the season in other habitats. Harmonia axyridis is an invasive and an intraguild predator present in high quantities in some specific crops. In these crops, H. axyridis could negatively impact on population of native species due to IGP observed in several other studies. [less ▲]

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See detailFirst evidence of a volatile sex pheromone in the invasive Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

Conference (2013, September 10)

Until now, volatile sex pheromone have not been identified in the Coccinellidae, although various studies have suggested the existence of such molecules. In this work, we have sampled volatile organic ... [more ▼]

Until now, volatile sex pheromone have not been identified in the Coccinellidae, although various studies have suggested the existence of such molecules. In this work, we have sampled volatile organic compounds released in the headspace of virgin females of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), that were either allowed or not to feed on pea aphids (Acyrthosiphon pisum Harris). When fed on aphids, virgin females showed a stereotypical “calling behavior”, commonly associated with the emission of a sex pheromone in several Coleoptera species. Behavioral assays conducted with calling females in a four-arm olfactometer demonstrated that the blend of released volatile compounds was attractive for males, but not for other females. The headspace of virgin females that were not previously fed with aphids was not attractive for either sex. GC-MS analyses revealed the presence of five compounds in the volatile blend: (–)-β-caryophyllene, β elemene, methyl-eugenol, α-humulene and α-bulnesene. Subsequently, we have collected and quantified the constituents from the blend over a period of 9 days after exposure to aphids. All five compounds were produced exclusively after feeding virgin females with aphids, and their quantity significantly increased during the whole period of collection. (–)-β-caryophyllene was found to be the major constituent, representing between 80 and 89 % of the total blend. These results could promote the development of more specific and efficient management methods to manipulate the movements of this invasive ladybeetle and to reduce its negative impacts on biodiversity. [less ▲]

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See detailSubstrate Marking by an Invasive Ladybeetle: Seasonal Changes in Hydrocarbon Composition and Behavioral Responses
Durieux, Delphine ULg; Fassotte, Bérénice ULg; Vanderplanck et al

in PLoS ONE (2013), 8(4),

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during the winter to survive the cold. Recent published reports have highlighted that overwintering individuals ... [more ▼]

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during the winter to survive the cold. Recent published reports have highlighted that overwintering individuals use hydrocarbon markings deposited on surfaces by conspecifics to orient toward aggregation sites. In the current study, monthly GC-MS analyses revealed seasonal modifications in the chemical profile of substrate markings deposited by moving individuals. The markings of overwintering ladybeetles contained larger proportions of heptacosadiene, nonacosadiene, hentriacontadienes, and methyl-nonacosanes, along with a lower proportion of heptacosene and nonacosene. This finding suggests the importance of the unsaturated and/or branched hydrocarbons in the H. axyridis aggregation process. Subsequently, we conducted behavioral assays to test whether (1) there is seasonal variation in the behavioral response of H. axyridis individuals toward substrate markings deposited by conspecifics in the same physiological state and (2) the observed behavioral modification is due to a change in ladybeetle sensitivity and/or a change in the chemical composition of the substrate marking. The results indicate that overwintering individuals exhibit a stronger ‘‘following’’ response toward conspecific substrate markings. This behavior is linked to both the physiological state of ladybeetles and the specific chemical profile of the marking biomolecules deposited under overwintering conditions. [less ▲]

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