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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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See detailAggregation behaviour of Harmonia axyridis
Durieux, Delphine ULg; Fischer, Christophe ULg; Fassotte, Bérénice ULg et al

in Bulletin OILB/SROP = IOBC/WPRS Bulletin (2013), 94

The multicoloured Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae), forms large aggregations inside dwellings to survive cold winters. The species’ migratory flight is well documented ... [more ▼]

The multicoloured Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae), forms large aggregations inside dwellings to survive cold winters. The species’ migratory flight is well documented. Harmonia axyridis preferentially moves towards prominent and visually contrasting elements (Obata, 1986; Nalepa et al., 2005). However, the mechanisms involved in the selection of aggregation sites are misunderstood. The work presented here was devoted to the study of chemicals used by H. axyridis during its aggregation process. During sampling of infested dwellings, non-volatile compounds were collected from aggregation sites. Gas chromatrography-mass spectometry (GC-MS) analyses showed that the chemicals found on the substrate where the beetles aggregate were different from the ones collected around these aggregation sites. These two blends are made up of the same long-chain hydrocarbons, comprising saturated and unsaturated homologues, but they are quantitatively different, the blend collected directly on the overwintering sites containing a higher proportion of saturated compounds than the other one. Behavioural experiments, involving overwintering H. axyridis individuals, were then conducted in the laboratory to understand the roles of these chemicals in aggregation. Firstly, an aggregation assay using the blend collected inside overwintering sites showed a clear preference of ladybeetles for areas containing these compounds, highlighting the retention capacity of the blend on H. axyridis. On the other hand, a Y-shaped tube assay, using the chemical blend found around the sites, showed that those compounds are used by male and female congeners as cues, allowing individuals to orientate towards the side of the set-up containing the tested chemicals. These results suggest the use of two different area markings by H. axyridis during its aggregation: the first one to lead congeners towards aggregation sites, and the second to ensure the cohesion of the cluster. Additional investigations were conducted to study the influence of (1) the presence of congeners and (2) the shelters’ luminosity on the H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in the laboratory under non-wintering conditions showed that the multicoloured Asian ladybeetles present a permanent aggregative behaviour, as a result of the existence of social interactions. These experiments also highlighted the clear preference of H. axyridis for dark shelters. [less ▲]

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See detailEtude des mécanismes responsables du comportement agrégatif d’Harmonia axyridis (Pallas) (Coleoptera : Coccinellidae)
Durieux, Delphine ULg

Doctoral thesis (2012)

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to ... [more ▼]

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to manage its populations. The social interactions involved in its aggregative behavior remain misunderstood although a better understanding of the semiochemicals the ladybeetles use during this phenomenon could lead to the development of new control methods. Therefore, the main objective of this thesis was to improve the understanding of the mechanisms set up by H. axyridis during its aggregative stage. Firstly, we have demonstrated the use of two different area markings by this species during its overwintering. The first one, laid by the ladybeetles while walking, lead conspecifics towards aggregation sites whereas the second one, deposited inside these sites, ensures the cohesion of the cluster. These markings are made up of saturated, mono- and diunsaturated hydrocarbons. Among these chemicals, it seems that the unsaturated hydrocarbons, and in particular the ones containing two double bonds, present a greater biological activity. However, the response of H. axyridis towards these chemicals depends on the insect physiological state. In the second instance, we have showed for the first time that H. axyridis presents a permanent aggregative behavior. The hydrocarbons laid by the ladybeetles during their displacements do not play any role in this behavior during summer conditions. On the other hand, conspecific elytral compounds and, in a lesser extent, physical contact, are well involved. Moreover, all our experiments have pointed out that visual elements play a major role in this social behavior and so, have also to be taken into account in the design of traps to control the populations of this invasive species. [less ▲]

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See detailHabitat diversity of the Multicolored Asian ladybeetle Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in agricultural and arboreal ecosystems: a review
Vandereycken, Axel ULg; Durieux, Delphine ULg; Joie, Emilie ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(4), 553-563

The Multicolored Asian ladybeetle, Harmonia axyridis (Pallas), native to Asia, is an invasive species in many European and American countries. Initially introduced as a biological control agent against ... [more ▼]

The Multicolored Asian ladybeetle, Harmonia axyridis (Pallas), native to Asia, is an invasive species in many European and American countries. Initially introduced as a biological control agent against aphids and coccids in greenhouses, this alien species rapidly invaded many habitats such as forests, meadows, wetlands, and agricultural crops. This paper reviews the habitats (forests, crops, herbs, gardens and orchards) where H. axyridis has been observed, either during insect samplings or as part of Integrated Pest Management (IPM) programs. Studies have referenced H. axyridis on 106 plant taxa (35 arboreal species, 21 crop species, 27 herbaceous species, 11 ornamental species, and 12 orchard species) and have identified 89 plant- prey relationships (34 arboreal species, 16 crop species, 13 herbaceous species, 10 ornamental species, and 16 orchard species) in different countries. Harmonia axyridis is more abundant in forest areas, principally on Acer, Salix, Tilia and Quercus, than in agroecosystems. Some plant species, such as Urtica dioica L., which surround crops, contain large numbers of H. axyridis and could constitute important reserves of this alien species in advance of aphid invasions into crops. This review highlights the polyphagy and eurytopic aspect of H. axyridis. [less ▲]

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See detailCharacterization of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) overwintering sites
Fassotte, Bérénice ULg; Durieux, Delphine ULg; Francis, Frédéric ULg et al

Poster (2012, August)

Originally introduced as a biological control agent, the multicoloured Asian ladybeetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), has become an invasive pest throughout Europe and North ... [more ▼]

Originally introduced as a biological control agent, the multicoloured Asian ladybeetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), has become an invasive pest throughout Europe and North America in the last few years. Although its effectiveness to control aphid and coccid populations was impressive, some negative impacts appeared rapidly, notably on human health. Indeed, to protect themselves from cold temperatures, H. axyridis individuals move inside dwellings and buildings and form large aggregations in concealed portions of structures to overwinter. The aggregating beetles are responsible for some annoyances due to, on one hand, the number of individuals inside homes and, on the other hand, the hemolymph secretions they release when they are disturbed, which can cause allergic reactions. In order to highlight the specific features of infested houses, we investigated a large number of overwintering sites in Wallonia between 2007 and 2011. These sites were characterized through a survey sent to homeowners confronted to invasion problems. This survey was mainly focused on a general description of the infested house (type, colour, infested floor(s), building material), the orientation of the colonized rooms and the position of the beetles’ cluster. The collected data indicate that H. axyridis preferentially selects isolated brick houses with red or white fronts to take shelter. Aggregations are mostly located at the first floor, essentially inside south, west or southwest oriented rooms. Furthermore, ladybeetles generally gathered into wooden windows frames facing south, west or southwest and to a lesser extent, in the upper corners of walls presenting the same orientation. All these results contribute to improve the knowledge on the aggregative behaviour of H. axyridis and could promote the development of more specific and efficient management methods to prevent massive infestations into dwellings, such as artificial shelters or trapping systems located at the outside of buildings. [less ▲]

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See detailBehavioral response of Harmonia axyridis towards their footprints according to their physiological state
Durieux, Delphine ULg; Fassotte, Bérénice ULg; Vanderplanck, Maryse et al

Poster (2012, August)

In order to survive cold, the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during winter. It has been recently highlighted that overwintering H. axyridis ... [more ▼]

In order to survive cold, the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during winter. It has been recently highlighted that overwintering H. axyridis individuals lay an area marking while walking, which is used by conspecifics to locate aggregation sites. These footprints are made-up of hydrocarbons, comprising both saturated and unsaturated homologues. However, it has not been demonstrated whether this “following area marking” behavior is specific to the overwintering individuals. The work presented herein was oriented to the study of the chemical evolution of these footprints according to the physiological state of H. axyridis. Monthly GC-MS analyses revealed that the area marking contained a greater amount of di-unsaturated compounds when laid by overwintering ladybeetles, suggesting the great importance of these chemicals in the ladybeetles aggregation process. In the second instance, behavioral investigations conducted in a Y-shaped glass tube were performed to assess (1) the evolution of H. axyridis behavior towards their footprints and (2) whether this behavioral modification is due to an evolution of the ladybeetles sensitivity or rather to an evolution of the area marking attractiveness. The results revealed that only the overwintering individuals follow their area marking, and that this behavior is linked to the ladybeetle physiological state rather than to the chemical profile of the marking biomolecules. [less ▲]

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See detailFlexible aggregative behavior of Harmonia axyridis according to the freshness of area marking in overwintering sites
Durieux, Delphine ULg; Fischer, Christophe ULg; Fassotte, Bérénice ULg et al

Poster (2012, July)

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), aggregates inside dwellings and buildings during winter to survive cold. This adaptive behavior causes annoyances ... [more ▼]

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), aggregates inside dwellings and buildings during winter to survive cold. This adaptive behavior causes annoyances to the occupants because of their large number and the induction of allergic reactions. Although this species has aroused a great interest these last years, the factors involved in the selection of its overwintering sites remain misunderstood. The work presented herein was oriented to the study of the non-volatile chemical compounds involved in this aggregation behavior. Chemical analyses revealed the occurrence, in aggregation sites, of an area marking made up of saturated and unsaturated hydrocarbons. Behavioral investigations demonstrated that H. axyridis preferentially aggregates in sites previously marked by congeners, indicating the retention potential of this blend on overwintering individuals. In the second instance, the same analyses were performed on an area marking aged of one year. The chemical investigations showed that only saturated hydrocarbons can still be detected after that period of time but the remaining blend does not induce aggregation anymore. This difference of response according to the freshness of the area marking suggests that this species would not be prisoner of the marking previously deposited on the substrate if the surrounding has changed and the site is not suitable anymore. [less ▲]

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See detailPhenology of the invasive coccinellid Harmonia axyridis Pallas and other aphidophages in crops
Vandereycken, Axel ULg; Durieux, Delphine ULg; Joie, Emilie ULg et al

Poster (2012, May 22)

The multicoloured Asian ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae), previously introduced as a biological control agent to control aphids populations, is now frequently considered as an ... [more ▼]

The multicoloured Asian ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae), previously introduced as a biological control agent to control aphids populations, is now frequently considered as an intraguild predator, consuming other aphids natural enemies. The interactions between this exotic ladybird and other aphidophagous species present in Belgian agro-ecosystems are mainly asymmetric in support of H. axyridis. An aphidophages sampling has been performed between 2009 and 2011 in four agrosystems such as broad bean, wheat, corn and potato. The sampling method consisted in the counting of aphids and all developmental stages of aphidophages present in quadrats of 1m² from April to September. Harmonia axyridis, the invasive coccinellid, was mainly observed in broad bean (21.84 ± 6.30 individuals/100m²) and corn (70.83±6.60 individuals/100m²) with other aphidophages such as Episyrphus balteatus (De Geer), Chrysoperla carnea sensus lato (Stephens), Coccinella septempunctata (Linné) and Propylea quatuordecimpunctata (Linné). In corn, our field data showed that immature stages and adults of H. axyridis were found throughout the summer. Adults were observed from mid-June to the beginning of September with two peaks, in the late June and in the beginning of August. The life history of larvae starts in late-June to the beginning of Augustus with only one peak (347.91 ± 59.99 individuals /100m²) in the beginning of July. The peak of H. axyridis arrives when no extraguild preys are present. At this moment, pupae of E. balteatus and C. septempunctata are the main food available to ensure the development of H. axyridis so that native aphidophages could be intraguild prey for H. axyridis. In the four crops, reproduction of H. axyridis starts after those of other aphidophages and so it does not benefit of available prey such as aphid: in corn and broad bean, C. septempunctata reproduce the first, in wheat it is E. balteatus and in potato it is C. carnea. That could be explained by several reasons: (1) H. axyridis reproduces firstly in arboreal habitats and after that comes in agrosystems, (2) the delay between aphidophage reproductions allows a reduction of interactions with other larvae during spring and therefore decrease mortality levels and (3) H. axyridis is able to use pollen as food substitute when no aphids are available. [less ▲]

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See detailFactors involved in the aggregation of Harmonia axyridis Pallas
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

Conference (2012, May 22)

In order to survive cold winters, the invasive multicoloured Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) forms large aggregations in dwellings to overwinter. The factors ... [more ▼]

In order to survive cold winters, the invasive multicoloured Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) forms large aggregations in dwellings to overwinter. The factors involved in the selection of aggregation sites remain misunderstood. The work presented herein focussed on the study of the chemical compounds involved in this phenomenon. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregation sites and ensure the cohesion of the cluster. Subsequently, physical factors were investigated. We studied the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory showed that the multicoloured Asian ladybeetles present a permanent aggregative behaviour, even during non-wintering conditions. These experiments also highlighted the existence of social interactions between individuals. All these results contribute to improve knowledge of this behaviour in H. axyridis and could be used in the design of species-specific traps in order to control infestations in dwellings. [less ▲]

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See detailAphid predators sampling in agrosystems in Belgium between 2009 and 2011
Vandereycken, Axel ULg; Durieux, Delphine ULg; Joie, Emilie ULg et al

Poster (2012, February 10)

The Multicolored Asian ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was imported in 1997 in Belgium to control aphid populations. Few years ago after its introduction, this exotic ... [more ▼]

The Multicolored Asian ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was imported in 1997 in Belgium to control aphid populations. Few years ago after its introduction, this exotic insect was well adapted to temperate climate conditions and spread out all over ecosystems in Europe causing decline of other aphidophagous species. In arboreal habitats, H. axyridis is the most dominant Coccinellids but we are still lacking information about this occurrence in agrosystems. An aphidophages sampling between 2009 and 2011 was realized in four agrosystems such as broad bean, wheat, corn and potato. Nevertheless H. axyridis populations rise (5 times) from 2009 to 2011 in 2011, H. axyridis is the third most observed aphidophages after Episyrphus balteatus (De Geer) and Coccinella septempunctata (Linné). H. axyridis is the dominating species in corn with 70.83±6.60 individuals per 100m². [less ▲]

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See detailCharacterization of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) overwintering sites
Fassotte, Bérénice ULg; Durieux, Delphine ULg; Haubruge, Eric ULg et al

Poster (2012, February 10)

The invasive multicoloured Asian ladybird, Harmonia axyridis (Pallas), forms large aggregations inside dwellings to overwinter. In order to highlight the specific features of infested houses, we ... [more ▼]

The invasive multicoloured Asian ladybird, Harmonia axyridis (Pallas), forms large aggregations inside dwellings to overwinter. In order to highlight the specific features of infested houses, we investigated a large number of overwintering sites in Wallonia between 2007 and 2011. These sites were characterized through a survey sent to homeowners confronted to invasion problems. The results indicate that H. axyridis preferentially selects isolated brick houses with red or white fronts to take shelter. Aggregations are mostly located at the first floor, essentially inside south or west oriented rooms. Furthermore, ladybirds generally gathered into wooden windows frames facing south or west, and to a lesser extent, in the upper corners of walls presenting the same orientation. [less ▲]

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See detailFast-GC quantifacation of harmonine, the major defense alkaloid of the multicolored Asian ladybird Harmonia axyridis (Pallas)
Fischer, Christophe ULg; Laurent, Pascal ULg; Heuskin, Stéphanie ULg et al

in American Journal of Analytical Chemistry (2012), 3

These last few years the multicolored Asian ladybird, Harmonia axyridis (Pallas), previously introduced in Europe and North America as a biological control agent, has swiftly spread out on those ... [more ▼]

These last few years the multicolored Asian ladybird, Harmonia axyridis (Pallas), previously introduced in Europe and North America as a biological control agent, has swiftly spread out on those territories and turns out to be a pest in several ways. In order to improve understanding of several key points of the biology of this ladybird, a novel fast-GC method of quantification of harmonine, the main defense alkaloid of H. axyridis, has been designed and validated using the accuracy profile concept for concentrations ranging from 13 to 264 µg/individual. This method allows quantifying harmonine in a single insect with a maximal error risk of 20%. For ladybirds collected in spring, mean harmonine concentration observed was 106.6 µg/individual with a very high standard deviation of 80.2 µg/individual, which can easily be explained by the strong asymmetry of the results distribution. Males and females seem equally chemically protected as the harmonine concentration did not significantly differ between sexes. This method is currently used to improve our comprehension of several key points of H. axyridis biology including aggregation behavior and aposematism. [less ▲]

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See detailFast-GC quantification of harmonine, the major defense alkaloid of the multicolored asian ladybird Harmonia axyridis (Pallas)
Fischer, Christophe ULg; Laurent, P; Heuskin, Stéphanie ULg et al

in American Journal of Analytical Chemistry (2012), 3

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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
Durieux, Delphine ULg; Vandereycken, Axel ULg; Joie, Emilie ULg et al

in Entomologie Faunistique = Faunistic Entomology (2012), 65

An inventory of the Coccinellidae present in the collection of the Department of functional and evolutionary Entomology (ULg - Gembloux Agro-Bio Tech) was performed on the period extending from 2001 to ... [more ▼]

An inventory of the Coccinellidae present in the collection of the Department of functional and evolutionary Entomology (ULg - Gembloux Agro-Bio Tech) was performed on the period extending from 2001 to 2009. This collection is essentially made up of insects collected by first year students. The aim of this work is to assess the evolution of the species belonging to this family with special interest in their relative amount and the species richness. This study was focused on the data from Wallonia and Brussels-Capital Region (Belgium), not enough insects having been collected in Flanders. Among the identified individuals, 27 species were observed, including 21 belonging to the subfamily of Coccinellinae, 2 to Epilachninae and 4 to Chilocorinae. Most of the species are native to Belgium. However, Harmonia axyridis (Pallas 1773), an exotic species coming from the South-East of Asia, was introduced in Belgium in 1997. This alien ladybird was firstly collected by the students in 2002 and the amount of collected individuals does not cease increasing until 2009. By contrast, a decrease of species richness, as well as the relative amount of Adalia bipunctata (L. 1758), Propylea quatuordecimpunctata (L. 1758) and Psyllobora vigintiduopunctata (L. 1758), is highlighted. The link between these evolutions is discussed. [less ▲]

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See detailRole of long-chain hydrocarbons in the aggregation behaviour of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Brostaux, Yves ULg et al

in Journal of Insect Physiology (2012)

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the ... [more ▼]

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the induction of allergic reactions. Migratory flight and macrosite choice of this species is well documented. H. axyridis shows a hypsotactic behaviour and a clear preference for contrasting visual elements. However, how the microsite is selected remains undocumented, although a better understanding of the implicated factors could lead to the development of new control methods for this pest. In this work, we have hypothesized that non-volatile compounds are involved in the microsite choice and the aggregation process of this beetle. Long chain hydrocarbons were identified inside aggregation sites, comprising saturated and unsaturated homologues. An aggregation bioassay was then conducted on overwintering individuals, highlighting the retention capacity of the previously cited compounds on the tested ladybeetles. Additional investigations have shown that H. axyridis males and females, originating from overwintering sites, deposit a similar blend of molecules while walking. A Y-shaped tube assay revealed that this blend is used by male and female congeners as cue, allowing individuals to orientate towards the treated side of the olfactometer. These results suggest the use of two different blends of long chain hydrocarbons by H. axyridis during its aggregative period, the first one to lead conspecifics towards aggregation sites (microsites) and the second to ensure the cohesion of the aggregation. These findings support the potential use of these blends, in association with volatiles, in the design of traps in order to control infestations of this species in dwellings. [less ▲]

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See detailStudy of the factors involved in the aggregation of Harmonia axyridis Pallas (Coleoptera : Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

in Communications in Agricultural and Applied Biological Sciences (2012), 77(1), 101-104

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in ... [more ▼]

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in the selection of its aggregation sites. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregations and ensure the cohesion of the cluster. On the other hand, we investigated the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory highlighted a permanent aggregative behaviour of H. axyridis, even during non-wintering conditions, and the existence of social interactions between individuals. [less ▲]

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