Contribution to French anthropophilic mosquitoes study : the particular cases of the genus Coquillettidia ; Contribution à l'étude des moustiques anthropophiles de France : le cas particulier du genre Coquillettidia.

Mosquito pest and disease vector populations are the main purposes of mosquito control and monitoring in France. In an historical study on malaria transmission in Alpine valleys, we pointed out that hydraulic developments should be considered as risk factors for vector-borne disease outbreaks. The evaluation of public perception of mosquito nuisance could help to adapt insecticidal treatments to people's expectations. Experience achieved in two sociological studies led us to propose the establishment of a mosquito pest survey based on the regular and combined uses of sociological tools and field sampling. Coquillettidia mosquitoes are a major nuisance and are difficult to control, since larvae live in a protected and deep habitat, attached to plant roots for their oxygen supply. The results of a large field study allowed us to inventory ecological indicators of Coquillettidia breeding sites, that can help to locate them. Aquatic plant species and kairomones emission (p-cresol, lauric and heptadecanoïc acids), water flow, salinity, turbidity, persistence of standing waters and impact of human operations must be involved in the choice of the breeding sites by these mosquitoes. Behavioral tests combined with chemical analysis enabled us to identify the mechanisms governing larval behavior of attachment to roots, determinant for their survival. It is proved that generalist semiochemicals (glycerol, uracil, thymine, uridine and thymidine) are involved in the host-plant identification by swimming larvae. Light intensity, oxygen concentration of water and roots morphology are also influencing larval attachment. Finally, a larvicidal strategy specially adapted to larval Coquillettidia ecology was set up. The capacity of aquatic plants to transport the systemic insecticide dimethoate via the phloem to the roots, and to release toxic compounds in larval surroundings has been proven. The high diminution (-85%) of larval attachment abilities increases the efficiency of this strategy. ; Les principaux enjeux de la gestion ...