Capacités de discrimination des femelles de quatre souches de Callosobruchus maculatus Fab. (Coléoptera : Chrysomelidae, Bruchinae) pour la localisation de l’hôte et la ponte aux dépens d’hôtes secondaires

L’objectif de cette étude est de savoir comment les femelles de quatre souches de Callosobruchus maculatus F., localisent leur hôte, distribuent les oeufs sur des graines de taille différente dans des conditions de libre choix, de semi choix et de non choix. Ainsi, des couples de C. maculatus ont été transférés du niébé, Vigna unguiculata (L.) Walp. (Fabaceae), et maintenus sur les graines de deux variétés de voandzou, Vigna subterranea (L.) Verdc. (Fabaceae), et du pois d’angole, Cajanus cajan (L.) Millsp (Fabaceae), trois ans durant. La capacité des femelles à reconnaître les odeurs de ces quatre types de graines a été testée à l’aide d’un olfactomètre et dans un dispositif tridimensionnel. Elles ont été ensuite mises en contact avec les différentes graines pour la ponte. Dans l’olfatomètre, lorsqu’elles ont le choix entre l’air pur et l’air provenant de leurs hôtes d’origine, elles sont significativement attirées par l’air odorant. Quand les femelles issues des souches du voandzou ou du pois d’angole ont le choix entre le niébé et leur plante d’origine, elles préfèrent le niébé. Dans le dispositif tridimensionnel, quand les femelles issues du voandzou ou du pois d’angole ont un libre choix entre les quatre types de graines, elles (> 30%) préfèrent leurs plantes hôtes d’origine. Les odeurs dégagées par les graines semblent contribuer à l’orientation des femelles vers ces graines. C. maculatus utilisent des signaux chimiques dans la localisation de leurs hôtes. Ceci entraînerait ou stimulerait l’utilisation des répulsifs et attractants dans la gestion intégrée des insectes de stocks.Mots clés: Capacités de discrimination, localisation, ponte, C. maculatus, plantes hôtes secondaire

Effets du remplacement de la farine de poisson par les termites (Macrotermes Sp.) sur l’evolution ponderale et les caracteristiques de carcasse de la volaille locale au Burkina Faso

The high cost and the accessibility of animal protein sources is a major issue in poultry farming in Burkina Faso. The present study aimed to assess the suitability of two termite species as feed for traditional chicken (Gallus domesticus) and guinea fowl (Numida meleagris), comparatively to commercial fishmeal available in this country. The study was carried out during eight weeks in Burkina Faso on ninety chickens and ninety guinea fowls, sixteen weeks old. Two termite species (dry Macrotermes subhyalinus and fresh Macrotermes bellicosus) and commercial fishmeal for poultry feed formulation that is available in the country were used as animal protein ingredients in three feeding management regimes. The birds were allocated to the three feeding treatments, with two replicates per treatment: i) treatment 1 (R1) with a diet including 2.5% of dried termites; ii) treatment 2 (R2) diet with no animal protein ingredient included, but with fresh termites given separately and the amount was depending on the daily capture; iii) treatment 3 (R3) diet including 2.5% of fishmeal. The results showed an average daily feed consumption of 65.5 g per bird. Average daily gain (ADG) for chickens was 7.7 g, 7.8 g and 7.5 g for treatment R1, R2 and R3, respectively. ADG for guinea fowl was 5.64g, 5.34 g and 5.35 g for R1, R2 and R3, respectively. Carcass characteristics studied on male guinea fowl showed a mean carcass percentage of 66.4%. Data on the taste and tenderness showed that R1 and R2 gave a better taste to guinea fowl meat, while R3 and R2 gave more tender meat. Average dry matter contents of the thighs were 42.4%, 41.8% and 40.6% for the groups R1, R2 and R3, respectively. No significant difference (p>0.05) was observed between treatments for all the parameters. Thus, dry and fresh Macrotermes spp. can be suitable animal protein ingredients that can substitute fishmeal in traditional chickens and guinea fowl feeding in rural area.Keywords: termites, fishmeal, feeding, local poultry, live weight performances, Burkina Fas

Precipitate Redistribution During Creep of Alloy 617

Nickel-based superalloys are being considered for applications within advanced nuclear power generation systems due to their high temperature strength and corrosion resistance. Alloy 617, a candidate for use in heat exchangers, derives its strength from both solid solution strengthening and the precipitation of carbide particles. However, during creep, carbides that are supposed to retard grain boundary motion are found to dissolve and re-precipitate on boundaries in tension. To quantify the redistribution, we have used electron backscatter diffraction and energy dispersive spectroscopy to analyze the microstructure of 617 after creep testing at 900 and 1000°C. The data were analyzed with respect to location of the carbides (e.g., intergranular vs. intragranular), grain boundary character, and precipitate type (i.e., Cr-rich or Mo-rich). We find that grain boundary character is the most important factor in carbide distribution; some evidence of preferential distribution to boundaries in tension is also observed at higher applied stresses. Finally, the results suggest that the observed redistribution is due to the migration of carbides to the boundaries and not the migration of boundaries to the precipitates

Influence of host origin on host choice of the parasitoid [i]Dinarmus basalis[/i]: Does upbringing influence choices later in life?

International audienceThe aim of this study was to investigate the influence of volatile compounds from four secondary host plants on the ability of [i]Dinarmus basalis[/i] Rond. (Hymenoptera: Pteromalidae) to locate, recognize, and parasitize its host, 4th instar larvae or pupae of [i]Callosobruchus maculatus[/i] F. ([i]Coleoptera: Chrysomelidae[/i]). To examine this, strains of [i]D. basalis[/i] were transferred from cowpea seeds [i](Vigna unguiculata[/i] (L.) Walp. (Fabales: [i]Fabaceae[/i])) to pigeon pea ([i]Cajanus cajan[/i] (L.) Millsp.) and two varieties of Bambara groundnut ([i]Vigna subterranea[/i] (L.) Verdc.) seeds. The ability of D. [i]basalis[/i] females to recognize the volatile compounds emanating from their complex host plant was tested by using a Y-tube olfactometer and a three-dimensional device. The results suggest that when females have a choice between pure air and the air emanating from their complex host of origin, they are attracted to the air tainted by the volatile compounds they have become accustomed to. They spent significantly more time (p < 0.0001) in the branch of the tube leading to the odorous air than in the tube leading to the pure air. When females from pigeon pea seed hosts were offered a choice between cowpea and pigeon pea seeds, all containing 4th instar larvae, the familiar odor of pigeon pea seeds were most attractive. When females from Bambara groundnut (white and striped) seed hosts were offered a choice between cowpea and pigeon pea seeds, all containing 4th instar larvae, they were significantly attracted to the odour of cowpea seeds. In the three-dimensional system, the females from the four strains did not appear to have any preference for a given type of seed containing 4th instar larvae or pupae. The parasitism rate remained high on all four types of seeds used. These results show that the use of D. [i]basalis[/i] as a biological control agent is possible in host changing situations where C. maculatus starts to attack other legumes. The results of this study also provide information supporting the behavioral plasticity of D. [i]basalis[/i]. Understanding the mechanisms involved in the adaptive phenomena of biological control agents is discussed in the context of the development of adequate methods of pest control