Tsetse flies, biodiversity and the control of sleeping sickness : structure of a Glossina guild in Southwest Côte d'Ivoire

Tsetse fly guilds usually comprise two or three species. However, the presence of only one species often indicates that anthropic modifications have occurred in the habitat. On the other hand, more than three species are seldom observed in the same zone and the presence of five is extremely rare. Previous detailed studies have always focused on a single species, without taking into account interactions between species. The authors present the results of observations carried out in Côte d'Ivoire on a guild consisting of #Glossina palpalis$, #G. pallicera$, #G. nigrofusca$, #G. longipalpis$ and #G. fusca$. #Glossina$ have unusual physiological characteristics : both sexes feed exclusively on blood, they have a highly developed larviparity associated with a slow rhythm of reproduction (one larva about every ten days) and a long life expectancy (up to nine months). The authors report on the size of the flies, the hosts, feeding habits, ecodistribution, resting-places, flying heights, circadian activity and seasonal dynamics of tsetse fly populations in order to understand the organization of this guild. Each species feeds indiscriminately on a wide spectrum of hosts without a particular preference. Different species shared habitat (ecodistribution) and time (circadian and annual cycles). Thus, during an annual cycle, there is always a slight time-lag between the density peaks of #G. palpalis$ and #G. pallicera$, the peak of the dominant species immediately preceding that of the dominated species. In a village area, 77% of the variations in density of #G. pallicera$ were accounted for by the previous variations in density of the dominant species (#G. palpalis$). Experiments show that #G. pallicera$ and #G. nigrofusca$ immediately invade anthropic areas from which #G. palpalis$ has been partially removed by trapping. These species thus appear to confront each other in a global dynamic equilibrium... (D'après résumé d'auteur