[Eco-distribution and Trypanosoma infection of Glossina palpalis palpalis in the Banco forest of and its relics, Abidjan (Côte d'Ivoire)]. / Chorologie et infection par les trypanosomes de Glossina palpalis palpalis dans la forêt du Banco et ses reliques, Abidjan (Côte d'Ivoire).

In order to implement an anti-vector programme in the suburb of Abidjan (Côte d'Ivoire), investigations were conducted to assess the tsetse fly densities as well as infection with trypanosomes. Catches were carried out during the rainy season and dry season with Vavoua traps laid during four consecutive days in different sites (Banco forest, Abidjan zoological park, area of the University of Abobo-Adjamé). One species of tsetse fly (Glossina polpalis palpalis) and two species of trypanosomes (Trypanosoma congolense, T. vivax) have been revealed. The apparent density per trap per day (DAP) is very high in the zoological park, 54.8 tsetse fly/trap/day during the dry season and 28.1 during the rainy season. At the University of Abobo-Adjamé, the DAP is respectively 13.5 and 8.1 tsetse fly/trap/day during the rainy season, and in the dry season it is only 0.9 and 0.8 in the Banco Forest. The physiological age on all sites is as follows: 57.5 % of old parous, 39% of young parous and 3.6 % of nulliparous in the rainy season. These proportions vary to 51.9% of young porous, 47.1% of old parous and 1% of nulliparous in the dry season. The overall infection rate is estimated at 20.7% in the rainy season and 20% in the dry season. Statistical analysis have showed a significant difference in the distribution of infection rates.

Sex ratio and female sexual status of the coconut pest, Oryctes monoceros (Coleoptera: Dynastidae), differ in feeding galleries and pheromone-baited traps.

Oryctes monoceros is a serious coconut pest, causing up to 40% damage in tropical Africa. Synthetic aggregation pheromone, ethyl 4-methyloctanoate, has been used to lure adults to traps. Traps with pheromone plus decaying palm material captured a high proportion of males. This raises the question whether individuals, which damage palms are receptive to the pheromone. We studied the sex ratio of the insects feeding on coconuts and those attracted to pheromone traps. Sixty two percent of adults from feeding galleries on living coconut palms were females. Pheromone with rotting palm material lured 43% females. To investigate the reasons for this difference, we compared the reproductive system of females lured to the odour traps or feeding in coconut galleries, or present in old rotting stems. Ninety six percent of the females trapped by pheromone had mated, and were sexually mature. In the galleries on living palms, 46% of females were immature, and 24% had not mated. In old rotting stems where eggs are laid and larvae develop, a mixture of 52% mated and 48% virgin females was found. Therefore, the pheromone together with the odour of rotting coconut stems signals a reproduction site to beetles, particularly mature females. In practice, the pheromone-baited traps will help in reducing the dissemination of gravid females, but will not affect directly the numbers of immature ones attacking palms. Our results show that when using pheromones for monitoring or controlling insects, the physiological status of the insects may have unexpected effects on the outcome.