First Polarimetric Investigation of Malaria Mosquitoes as Lidar Targets

In this paper, we use a novel spectral polarimetric optical tomographic imaging goniometer to investigate the scattering properties of Anopheles malaria mosquitoes to aid in their detection and identification in entomological lidar applications. Mosquitoes were mounted on a turn table, on which they were illuminated from different angles with linearly polarized near-infrared light and rotated. Thus, aspect-dependent optical cross sections were retrieved in backscatter and extinction mode. The backscattering and extinction properties of male and female mosquitoes were further condensed into a pair of parameters. We investigate the wings and bodies of mosquitoes together and independently, and conclude that the wings of mosquitoes strongly scatter copolarized light and that the degree of linear polarization of light scattered by insect bodies is independent of the aspect. In lidar measurements, light scattered by insect wings can be separated from light scattered by insect bodies due to the oscillatory wing beats. Therefore, obtaining the scattering properties of bodies and wings independently is of particular interest. Finally, we conclude that 808 nm light is well suited for detecting specular reflexes produced by Anopheles wings, which has large implications for the design of entomological lidar instruments used to study malaria mosquitoes.