author(s)
D Watching, BR Tamgno, IE Nkenmogne Kamdem, M Zilbinkaye, LS Ngamo Tinkeu and MB Ngassoum

abstract
Volatile organic compounds (VOCs) contribute significantly to food flavor and can be used as indicators to female parasitoids to locate resources like hosts or preys to lay eggs or to feed. Chemical signals play a key role in trophic relationship. Callosobruchus maculatus’ parasitoids select specific stage larvae of their host as egg-laying sites. The most useful tools to avoid the loose of post-harvest’s grains are chemical pesticides. The main objectives of this work concern a characterization of the odours attracting parasitoids to increase their numbers and to reduce use of pesticides harmful to the environment and human health. Experiments were carried out to find out among VOCs release by C. maculatus which attract parasitoids. A set of 100 larvae of C. maculatus and 3 g of their feces collected from infested seeds at each stage of larvae were separately kept in 10 ml vials. These samples were exposed at the end of olfactometer for choice of the parasitoids females and analyzed by solid phase micro-extraction (SPME) coupled with gas chromatography-flame ionization detection (GC-FID) and gas chromatography–mass spectrometry (GC-MS). A four arms olfactory test revealed that Dinarmus basalis females were more attracted to larvae IV of C. maculatus; Anisopteromalus. calandrae females were more attracted to the frass and the nymphs’ odours elicited significantly greater response in Eupelmus vuilleti females than the others.The GC-MS analysis show particularly that 4-Octen-3-one and 1-Octen-3-ol were emitted by the odors’ nymphs; 2-Hexen-1-ol and 5-Methyl-4-Hepten-3-one was produced by the frass and 2-Methylpyrazine was specific to the larvae IV. This provides, for the first time, these specific molecular bases for host could be the location’s odors’ by the hymenopteran parasitoids.