Mosquitoes can spread cholera from water to water. They orient themselves by polarized light. Photo: Fritz Geller-Grimm
Reading Mosquitoes will find the most favored waters for oviposition on the basis of polarized light, which is reflected from the water surface. Researchers from Israel discovered this when they lured the mosquitoes into a tent with differently lit pools of water. The insects are notorious for carrying the cholera bacterium from water surface to water surface. In their experiments, the researchers had the mosquitoes choose between four water bowls. Two of the bowls were illuminated with polarized light, in which the light waves oscillate in one plane, the other two with unpolarized light, as it is also emitted by the sun. In order to measure the influence of light intensity on the mosquitoes, researchers in each group used one intense and one diminished light source. The mosquito mothers clearly preferred the pools of light illuminated with polarized light, while the one with the higher intensity was the most popular, the analysis showed.

This result coincides with the observation that mosquitoes do not randomly choose the water for oviposition, but prefer cloudy, dark waters with as many nutrients as possible. Dark areas return the light polarized to a higher percentage than bright areas because they only reflect waves with a certain orientation but absorb others.

Mosquitoes can perceive this directional light and thus explore suitable oviposition sites, the researchers explain. This is also supported by the results of a second experiment, in which the researchers used different cloudy water. Again, the female mosquitoes preferred the darkest water for oviposition, as this returned the highest percentage of polarized light, making it the most nutritious nursery for the female.

Mollusks are a common mosquito family closely related to the mosquitoes. The name derives from the convulsions that the animals perform in peace. Although these insects do not sting, they spread the bacterium Vibrio cholerae, which is dangerous for humans and can be absorbed through contaminated drinking water. display

Amit Lerner (Hebrew University Jerusalem, Israel) et al .: Journal on Experimental Biology, Vol. 211, p. 3536 ddp / Stefan Pröll


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