Multiband modulation spectroscopy for the determination of sex and species of mosquitoes in flight

Abstract

We present a dual-wavelength polarimetric measurement method to distinguish species and sexes of disease transmitting mosquitoes in flight. By measuring co- and de-polarized backscattered light at 808 and 1550 nm, the degree of linear polarization, wingbeat frequency, reflectance, spectral ratio and glossiness of mosquitoes can be retrieved. Body and wing contributions to these signals can be separated. Whereas the optical cross section is sensitive to the aspect of observation, thus the heading direction of the insect in flight, we demonstrate that polarimetric- and spectral-band ratios are largely invariant to the aspect of observation. We show that wing glossiness, as well as wing- and body-spectral ratios are particularly efficient in distinguishing Anopheles coluzzii and Anopheles arabiensis, 2 closely related species of malaria vectors. Spectral and polarimetric ratios relate to microstructural and melanization features of the wing and body of these species. We conclude that multiband modulation spectroscopy is a useful expansion of the parameter space that can be used to improve the specificity of entomological lidars.

Can the narrow red bands of dragonflies be used to perceive wing interference patterns?

“…Our group has a previously remotely measured backscatter from airborne insects with kHz sample rates (Brydegaard, 2015;Brydegaard, Gebru, & Svanberg, 2014; Brydegaard, Merdasa, Gebru, Jayaweera, & Svanberg, 2016;Gebru, Brydegaard, Rohwer, & Neethling, 2016;Malmqvist, Jansson, Torok, & Brydegaard, 2016 (Gebru et al, 2018).…”

Photonic Monitoring of Atmospheric and Aquatic Fauna

“…Generally, there is a massive advantage of detecting different scattering from 0.1% to 1% as opposed to detecting an extinction from 99.9% down to 99%. In point monitors and laboratory setups, multiple angular modes of side scatter and extinction can easily be added . In lidar, extinction can be estimated by the reduction in the post‐echo compared to the static value .…”

“…This is because lateral transport dominates over vertical transport and the anatomical axes are predominantly horizontal such that optical cross sections remain invariant with heading angle. Also certain band ratios such as depolarization or melanization have been shown to be largely angular insensitive . The increased scatter from ventral observations can also be exploited to derive body orientation .…”

“…The frequencies are somewhat characteristic to the species, perhaps more in entomology than in ornithology. In particular, sexes are known to differ considerably, for example, for mosquitoes . However, the fundamental frequency is temperature dependent, and temperature coefficients are different for different species.…”

“…The harmonic spectrum for an individual depends on the aspect of observation, and vertical probing greatly cancels out these geometrical challenges . The modulation content can also differ between spectral bands because of different pigmentation on different body parts . The flat and sometimes glossy wing membranes of insects can produce specular spikes on the wing‐beat waveform.…”