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See detailAnalyse de la faune entomologique associée à Jatropha curcas L. dans la région de Maradi au Sud-est du Niger
Abdoul Habou, Zakari; Toudou, Adam; Haubruge, Eric ULg et al

in Entomologie Faunistique = Faunistic Entomology (2013), 66

Jatropha curcas L. is a shrub belonging to the Euphorbiaceae family. It is cultivated in Africa as living fence, and for its seeds, rich in oil that can be used as Biofuel. The inventory of insects ... [more ▼]

Jatropha curcas L. is a shrub belonging to the Euphorbiaceae family. It is cultivated in Africa as living fence, and for its seeds, rich in oil that can be used as Biofuel. The inventory of insects associated with these shrubs present in Maradi (South-eastern Niger) was conducted by combining beating, trapping and visual observation methods. The inventories were carried out from July to September 2010 and were repeated at the same period in 2011. A total of 1761 insects were collected on J. curcas. These insects belong to 45 different species belonging to 30 families. Coleopterans are the most numerous with 32% of captured insects, followed by Hymenopterans (24%), Orthopterans (14%), Dipterans (13%), Heteropterans (10%) and Isopterans (4%). Among the captured insects, only Heteropterans, Orthopterans and some Coleopterans can cause damage to J. curcas in Niger. [less ▲]

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See detailMicroorganisms and semiochemicals as control strategies against phytophagous insect pests
Verheggen, François ULg

Conference (2013)

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their ... [more ▼]

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their dispersal in natural environment. Here we report the isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which acts as a kairomone enhancing the efficiency of aphid natural enemies, both in the laboratory and in potato fields. Our findings represent the first case of a host-associated bacterium driving prey location and ovipositional preference for the natural enemy. We show that this bacterium has a key role in tritrophic interactions because it is the direct source of volatiles used to locate prey. Some specific semiochemicals produced by S. sciuri were also identified as significant attractants and ovipositional stimulants. The use of this host-associated bacterium could certainly provide a novel approach to control aphids in field and greenhouse systems. [less ▲]

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See detailMicroorganisms from aphid honeydew attract natural enemies and tending ants
Verheggen, François ULg

Scientific conference (2013)

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See detailLes vers à soie de la famille des Psychidae : évaluation de leur nombre et des connaissances locales associées à l’exploitation de leur soie, dans la commune d’Arivonimamo
Hecq, Florence; Razafimanantsoa, Tsiresy; Haubruge, Eric ULg et al

in Verheggen, François; Bogaert, Jan; Haubruge, Eric (Eds.) Les vers à soie malgaches : Enjeux écologiques et socio-économiques (2013)

Tapia woods (Uapaca bojeri) are endemic to Madagascar and provide the locals with resources that are usually associated with important financial inputs. Among these resources, silk moths are developing in ... [more ▼]

Tapia woods (Uapaca bojeri) are endemic to Madagascar and provide the locals with resources that are usually associated with important financial inputs. Among these resources, silk moths are developing in tapia woods including Borocera cajani, locally named landibe. B. cajani silk is widely used in Malagasy tradition. These woods also provide habitat for other less known silk moth species, including those belonging to the Psychidae family. Two objectives were defined in the present study: (1) The evaluation of Psychidae populations in Arivonimamo through an entomological inventory and (2) the determination of the role of Psychidae in the life of local population. We also have extracted silk from Psychidae silk moth. Insect inventories conducted from February to May 2010 show that the numbers of Psychidae do not vary significantly during the inventoried period, and that between 2 and 26 individuals are observed per 1,000 m2. Almost all interviewed people underline that Psychidae silk is no longer exploited. By applying, on Psychidae cocoons, the silk extraction method usually applied on landibe, we were able to obtain silk. [less ▲]

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See detailAphid responses to volatile cues from turnip plants (Brassica rapa) infested with phloem-feeding and chewing herbivores
Verheggen, François ULg; Haubruge, Eric ULg; De Moraes, Consuelo et al

in Arthropod-Plant Interactions (2013), 7(5), 567-577

Herbivore-induced plant volatiles provide foraging cues for herbivores and for herbivores’ natural enemies. Aphids induce plant volatile emissions and also utilize plant-derived olfactory volatile cues ... [more ▼]

Herbivore-induced plant volatiles provide foraging cues for herbivores and for herbivores’ natural enemies. Aphids induce plant volatile emissions and also utilize plant-derived olfactory volatile cues, but the chemical ecology of aphids and other phloem-feeding insects is less extensively documented than that of chewing insects. Here, we characterize the volatile cues emitted by turnip plants (Brassica rapa) under attack by an aphid (Myzus persicae) or by the chewing lepidopteran larva Heliothis virescens. We also tested the behavioral responses of M. persicae individuals to the odors of undamaged and herbivore-damaged plants presented singly or in combination, as well as to the odor of crushed conspecifics (simulating predation). Gas chromatographic analysis of the volatile blend of infested turnips revealed distinct profiles for both aphid- and caterpillar- induced plants, with induced compounds including green-leaf alcohols, esters, and isothiocyanates. In behavioral trials, aphids exhibited increased activity in the presence of plant odors and positive attraction to undamaged turnip plants. However, aphids exhibited a strong preference for the odors of healthy versus plants subjected to herbivore damage, and neither aphid- or caterpillar-damaged plants were attractive compared to clean-air controls. Reduced aphid attraction to herbivore-infested plants may bemediated by changes in the volatile blend constituent composition, including large amounts of isothiocyanates and green-leaf volatiles or, in the case of aphid-infested plants, of the aphid alarm pheromone, (E)-b-farnesene. [less ▲]

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See detailActivité journalière et comportement d’alimentation de Borocera cajani Vinson 1863 (Lepidoptera: Lasiocampidae) sur deux de ses plantes hôtes : Uapaca bojeri Baillon 1874 et Aphloia theiformis (Vahl) Bennett 1840
Razafimanantsoa, Tsiresy; Raminosoa, Noromalala; Rakotondrasoa, Olivia et al

in Entomologie Faunistique = Faunistic Entomology (2013), 66

Borocera cajani Vinson 1863 (Lasiocampidae) or "Landibe" is a wild silk-moth, which silk is the most widely used in the textile industry in Madagascar. This endemic species is found throughout the island ... [more ▼]

Borocera cajani Vinson 1863 (Lasiocampidae) or "Landibe" is a wild silk-moth, which silk is the most widely used in the textile industry in Madagascar. This endemic species is found throughout the island, but colonizes especially the "Tapia" forest in the central highlands. The species has an important economic, culinary and cultural role in the Island. It is polyphagous and frequents several host plants. The daily activity of the larvae of B. cajani has been studied in their natural habitat on two native host plants of the "Tapia" forest: Uapaca bojeri Baillon 1874 (Phyllanthaceae) and Aphloia theiformis Bennett 1840 (Flacourtiaceae). Continuous observations during 24 hours on 54 individuals of the last instar of B. cajani have been conducted. Daily period of activity were found to vary according to the host plant species. Larvae feeding on U. bojeri allocate 6.9% of their time to feed, while the larvae feeding on A. theiformis spend 3.3% of their time. Only 1.0% (15 minutes) and 0.7% (10 minutes) of the observed period was allocated to movement, in the larvae feeding on U. bojeri and A. theiformis, respectively. Larvae observed on A. theiformis took an average of 3.1 ± 0.2 meals a day, which lasted 15.4 ± 1.3 min. Larvae observed on U. bojeri took an average of 1.9 ± 0.1 meals a day, which lasted 54.8 ± 5.2 min. [less ▲]

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See detailInfluence de la plante hôte sur les stades de développement de Borocera cajani (Lepidoptera: Lasiocampidae)
Razafimanantsoa, Tsiresy; Malaisse, François ULg; Raminosoa, Noromalala et al

in Entomologie Faunistique = Faunistic Entomology (2013), 66

Borocera cajani Vinson (Lepidoptera: Lasiocampidae) is a silk moth endemic to Madagascar that is currently used to produce silk textiles. This silk moth is polyphagous and colonizes forests situated in ... [more ▼]

Borocera cajani Vinson (Lepidoptera: Lasiocampidae) is a silk moth endemic to Madagascar that is currently used to produce silk textiles. This silk moth is polyphagous and colonizes forests situated in the central highlands, mainly constituted by Tapia trees (Uapaca bojeri). Two host plants are commonly used by the caterpillar of this moth species: Tapia and Voafotsy (Aphloia theiformis). In this work we have evaluated parameters of different stage (survival rate, development duration, weight and size, fecundity…) of B. cajani on both host plants. We have observed a 30% higher survival rate on U. bojeri. Larval and pupae duration were shorter on U. bojeri (64,8 ± 1,5 days) than on A. theiformis (87,4 ± 2,0 days). Cocoons were bigger when obtained from larvae fed on U. bojeri. This plant is therefore better for the development of B. cajani and should be used in intensive rearing of this silk moth. [less ▲]

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See detailSilkworm moths inventory in their natural tapia forest habitat (Madagascar): diversity, population dynamics and host plants
Razafimanantsoa, Tsiresy; Raminosoa, Noromalala; Rakotondrasoa, Olivia et al

in African Entomology (2013), 21(1), 137-150

Endemic silk moths (Lepidoptera: Lasiocampidae) in Madagascar have been collected and exploited for centuries by local populations either for food or as a source of silk cocoons from which textiles are ... [more ▼]

Endemic silk moths (Lepidoptera: Lasiocampidae) in Madagascar have been collected and exploited for centuries by local populations either for food or as a source of silk cocoons from which textiles are made. Moth natural forest habitat has also been degraded, leading to a drastic decrease in silk moth populations. However, very few scientific reports highlighted these observations well known by the local people.We have inventoried silk moths species in tapia (Uapaca bojeri Baill.) forests located in the central highlands of Madagascar. Inventories have been conducted during one year from August 2009 to July 2010 by sampling transects in Imamo forests. Three species of Lasiocampidae belonging to two genera were found: Borocera cajani Vinson, Borocera marginepunctata Guérin-Méneville and Europtera punctillata Guenée. These three silk moth species are endemic to Madagascar but only one (B. cajani) is commercially exploited in the silk industry. The habitat, host plants, abundance, life cycle and feeding behaviour of these species in their natural habitat are described. [less ▲]

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See detailOccurrence of Harmonia axyridis (Coleoptera: Coccinellidae) in field crops
Vandereycken, Axel ULg; Brostaux, Yves ULg; Joie, Emilie ULg et al

in European Journal of Entomology (2013), 110(2),

Abstract. The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. This study focuses on the occurrence of ... [more ▼]

Abstract. The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. This study focuses on the occurrence of this exotic species and its seasonal abundance in various field crops. The abundance of adults, larvae and pupae of H. axyridis was evaluated over a three-year period, from 2009 to 2011, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. From May to September, 48 1-m² quadrats were visually inspected in each of the fields sampled on several farms every seven days. H. axyridis colonized and reproduced in all of the four crops studied, with the largest numbers recorded in corn and broad bean crops. Larvae and adults of H. axyridis were recorded mainly in corn and to a much less extent in wheat and potato crops. From 2009 to 2011, the mean weekly abundance of H. ayxridis remained constant except in corn crops, where the recorded densities of all the immature stages and adults were higher in 2011 than in 2009. The population dynamics of aphids and H. axyridis are well described by a symmetric logistic function (S-shape) of cumulative population size. 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 start 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. [less ▲]

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See detailChemical Ecology of the Colorado Potato Beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), and Potential for Alternative Control Methods
Sablon, Ludovic ULg; Dickens, Joseph C.; Haubruge, Eric ULg et al

in Insects (2013), 4(1), 31-54

The Colorado potato beetle (CPB) has been a major insect pest to potato farming for over 150 years and various control methods have been established to reduce its impact on potato fields. Crop rotation ... [more ▼]

The Colorado potato beetle (CPB) has been a major insect pest to potato farming for over 150 years and various control methods have been established to reduce its impact on potato fields. Crop rotation and pesticide use are currently the most widely used approaches, although alternative methods are being developed. Here we review the role of various volatile and nonvolatile chemicals involved in behavior changes of CPB that may have potential for their control. First, we describe all volatile and nonvolatile chemicals involved in host plant localization and acceptance by CPB beetles, including glycoalcaloids and host plant volatiles used as kairomones. In the second section, we present the chemical signals used by CPB in intraspecific communication, including sex and aggregation pheromones. Some of these chemicals are used by natural enemies of CPBs to locate their prey and are presented in the third section. The last section of this review is devoted a discussion of the potential of some natural chemicals in biological control of CPB and to approaches that already reached efficient field applications. [less ▲]

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See detailAbundance and phenological model of Harmonia axyridis (Coleoptera: Coccinellidae) in field crops
Vandereycken, Axel ULg; Brostaux, Yves ULg; Joie, Emilie ULg et al

Poster (2012, December 07)

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive ... [more ▼]

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive principally in shrubs and arboreal habitats. We focus on a phonological model and on annual abundance in various field crops. The abundance of H. axyridis adults and larvae were evaluated during a three-year period, from 2009 to 2011, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. H. axyridis colonizes and reproduces in all four crops studied, with larger densities observed in corn and broad bean. The reproduction of H. axyridis occurs principally in corn and occurred much less in wheat and potato. From 2009 to 2011, abundances of H. axyridis populations were constant except in corn, where the observed densities of all immature stages and adults were higher in 2011 than in 2009. The population dynamics of aphids and H. axyridis were characterized by a symmetric logistic function (S-shape) based on the cumulative population size. [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 detailChoosing an aphid partner: a matter of taste and smell
Detrain, Claire; Fischer, Christophe ULg; Lognay, Georges ULg et al

Conference (2012, August 27)

Honeydew is the keystone upon which ants and aphids build their mutualistic relationship. We have investigated how sugar and volatile compounds from honeydew are involved in the discovery, the recognition ... [more ▼]

Honeydew is the keystone upon which ants and aphids build their mutualistic relationship. We have investigated how sugar and volatile compounds from honeydew are involved in the discovery, the recognition and the exploitation of aphid colonies by the black garden ant Lasius niger. In addition to semiochemicals produced by aphids, honeydew volatile compounds are used by ant scouts to orient themselves and distantly recognize myrmecophilous species. Once discovered, aphid colonies producing sugars which are the most beneficial to the ants are preferentially tended. In this respect, the ways each sugar acts upon the feeding behavior of ant foragers and triggers the laying of a recruitment trail are essential to understand how their collective exploitation of aphid colonies proceeds and why mutualistic interactions between ants and aphids are maintained. Sensitivity of ant scouts to honeydew sugars was also investigated. Dose-response curves revealed between-sugar differences with foragers being very sensitive even to small amounts of melezitose, a sugar specifically produced by aphid colonies. We discuss about the relevance of honeydew cues used by ants in the selection of sugary resources, the recognition of their honeydew-producing partners as well as in the assessment of size and nutritive value of exploited aphid colonies. [less ▲]

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See detailVolatile organic compounds released by barley roots attract wireworms
Barsics, Fanny ULg; Fiers, Marie ULg; Francis, Frédéric ULg et al

Poster (2012, August)

Wireworms, the soil dwelling larvae of click beetles, are pests of many crops worldwide. Alternatives to insecticide treatments are needed for integrated management strategies. Our work consists in ... [more ▼]

Wireworms, the soil dwelling larvae of click beetles, are pests of many crops worldwide. Alternatives to insecticide treatments are needed for integrated management strategies. Our work consists in elucidating the role of barley (Hordeum vulgare L.) root-emitted volatile organic compounds (VOC) on the orientation behaviour of Agriotes sordidus Illiger wireworms (Fig. 1). Using dual choice olfactometers, we have evaluated the attractiveness of baits ranging from barley roots themselves to one isolated root-emitted volatile organic compound. [less ▲]

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See detailHoneydew volatile emission acts as a kairomonal message for the Asian lady beetle Harmonia axyridis (Coleoptera: Coccinellidae)
Leroy, Pascal; Heuskin, Stéphanie ULg; Sabri, Ahmed ULg et al

in Insect Science (2012), 19(4), 498-506

The Asian lady beetle Harmonia axyridis Pallas is considered as an invasive species in most territories where it has been introduced. Because aphid honeydew acts as an attractant for many aphid predators ... [more ▼]

The Asian lady beetle Harmonia axyridis Pallas is considered as an invasive species in most territories where it has been introduced. Because aphid honeydew acts as an attractant for many aphid predators and parasitoids, the objectives of this work were to collect and identify the volatile compounds released from the aphid excretory product to evaluate how these semiochemicals could affect the H. axyridis foraging behavior. Twelve volatile chemicals were identified from the Megoura viciae Buckton honeydew including four alcohols, three ketones, three aldehydes, a pyrazine and a monoterpene. The volatiles 3-methyl-1-butanol and 3-methyl-butanal were highlighted as the two most abundant semiochemicals released from the M. viciae honeydew. Vicia faba L. plants treated with crude honeydew attracted more than 80% of the tested individuals with 40% of attracted beetles located on the plant. Four volatile compounds (3-hydroxy-2-butanone, 3-methyl-butanal, 3-methyl-1-butanol and limonene) were also highlighted to attract more than 75% of the coccinellids toward the odor source and to locate about 35% of them on the plants. Limonenewas the most efficient attractant since 89% of the H. axyridis responded to this odor. The use of the identified semiochemicals aswell as the composition of an artificial honeydew could certainly be helpful to control the dispersal of the Asian lady beetle 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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