author(s)
Maha Kalboussi, Mohamed Elimem, Thameur Bouslama, Chaima Lahfef, Essia Limem-Sellemi and Slim Rouz

abstract
The Aphididae family contains many polyphagous species. Four species were identified in an organic Citrus orchard in Northeastern Tunisia in the current study. These species are Aphis gossypii, A. spiraecola, Macrosiphum euphorbiae, and Toxoptera aurantii. The most important and abundant species was A. gossypii followed respectively by A. spiraecola, M. euphorbiae, and T. aurantii. Monitoring species dynamic population showed that aphids began to occur in February and reached then high levels from March to May. Various structure and beta diversity indexes were calculated. The obtained results demonstrated that there was a high dominance of a few or one species. The evenness index was high and had a significant positive correlation with the Berger-Parker index. The Equitability index was low. The richness index had a strong positive correlation with Margalef’s richness index and the number of species. However, Menhinick's diversity index had a weak positive relationship with the Specific richness.