At all four sites, 100 300 of B. invadens were recorded per trap per week at the end of August/beginning September 2008, and this consistently decreased thereafter to less than 50 flies per trap per week in December 2008. The population hovere around this low value through April 2009. From that point on, the population began increasing to reach a peak of more than 600 flies per trap per week in June, except in Glo- Djigbé, Abomey-Calavi where it peaked at around 400. The highest population of D bivittatus was mostly recorded in November.