Introduction. Since its arrival in Senegal in 2004, Bactrocera invadens (Diptera Tephritidae) synonymized with Bactrocera dorsalis has caused much economic damage in mango crops. Effective and efficient control activities against B. invadens were necessary in order to continue mango production, and biological control measures were envisaged. In such conditions, the government of Senegal allowed the Asian parasitoid Fopius arisanus to be released in some orchards around Ziguinchor. Materials and methods. The dynamics of fruit fly species was studied with lure traps (methyl eugenol and terpinyl acetate with Dichlorvos). Mango fruit were sampled from the control orchard and orchards with released F. arisanus, to compare the differences in tephritid infestation. Results and discussion. The levels of B. invadens populations were 1.6−2.5 times higher in the control than in orchards where F. arisanus was released. The fruit were also 5-6 times more infested in the control orchard than in those that received F. arisanus. Between May and July 2012 the majority of the pupae (92%) collected from fruit samples developed into adult flies, while only 39% of the pupae transformed to adults between October and December after effective action of the parasitoids. In both orchard treatments, the level of native fruit fly populations was about the same. Wild fruit were infested mostly by Ceratitis cosyra, from which were reared native parasitoids such as Fopius caudatus, F. silvestrii, F. desideratus, Diachasmimorpha fullawayi, D. carinata, Psyttalia cosyrae, and P. concolor. In contrast with Mangifera indica, Citrus spp., Anacardium occidentale, Psidium guayava, Saba senegalensis, and Landolphia heudelotii were mainly infested by B. invadens which showed parasitism by F. arisanus. Pteromalidae and Eulophidae were also found from the pest fly pupae. Killer flies (Diptera: Muscidae) such as Coenosia attenuata Stein, C. atra Meigen and C. tigrina Fabricius emerged from the fruit samples. Conclusion. Sanitation against fruit flies in Casamance should take into account the conservation of natural enemies such as parasitoids and predators for an effective biological control of tephritids. Keywords: Senegal / Casamance / Mangifera indica / mango / fruit fly / Bactrocera invadens / Fopius arisanus / biological control Résumé-Enquêtes préliminaires après lâcher du parasitoïde de la mouche des fruits Fopius arisanus Sonan (Hyménoptère, Braconidae) dans des plantations de manguiers en Casamance (Sénégal). Introduction. Depuis son introduction au Sénégal en 2004, Bactrocera invadens (Diptère, Tephritidae) synonyme de Bactrocera dorsalis, a causé d'énormes dégâts économiques aux cultures de manguiers. Des mesures réelles et efficaces de lutte contre B. invadens se sont avérées indispensables pour continuer à produire des mangues, et des méthodes de lutte biologique ont été envisagées. Dans ces conditions, le gouvernement du Sénégal a autorisé l'importation du parasitoïde asiatique Fopius arisanus afin de le lâcher dans quelques vergers autour d...