The impact of biological invasions of insects considered as pests have important negative impacts on the economy and the environment, particularly in insular ecosystems. Since the detection of one of the most harmful pest of fruit and vegetable crops, Bactrocera dorsalis, in April 2017, La R´eunion counts nowadays nine pests species of Tephritid fruit ¿ies of economic importance. A biological control agent, the braconid wasp, Fopius arisanus, was initially introduced in La Reunion in 2003 to control another fruit ¿y of the same genus: the peach fruit ¿y, Bactrocera zonata. Bactrocera dorsalis, in its native area is the main host of this braconid wasp and will probably be able to parasitize it in La R´eunion. To understand the invasion process of B. dorsalis and the impact of this new introduced fruit ¿y on the community structure of the resident Tephritid species, and the parasitoid, F. arisanus, it is necessary to study the competition interactions. We ¿rst assessed the interspeci¿c competition between Bactrocera dorsalis and four other fruit ¿ies, Bactrocera zonata, C. capitata, C. quilicii and Ceratitis catoirii. Three of those fruit ¿ies are successive invaders in La Reunion and one endemic species. We focused our study on the interference competition among pairs of adults, measuring the ability of a female to remove another one from a fruit for the laying behavior in controlled environments.The parasitoid preference for both sympatry species of genius Bactrocera were observed. On one hand, we observed the preference for eggs only and on the other hand, the preference for one particular species according to the host fruit in choice experiments.