Influence of ground marker shape on Anopheles coluzzii swarm spatial structure and flight kinematics: a 3D video-tracking study

Abstract Mating in Anopheles mosquitoes depends on swarming, in which males aggregate at dusk above visual ground markers and females enter to copulate. Ground markers are known to anchor swarm location, yet whether marker geometry influences swarm spatial structure and individual flight dynamics remains unquantified. We combined semi-field experiments with 3D infrared video-tracking to test how ground marker shape affects swarm organization and flight behavior in Anopheles coluzzii . Five marker shapes of 1 m² each were tested in semi-field (Bama, Burkina Faso), yielding 7,060 swarming trajectories across 20 recordings. Swarms centroid position remained stable across marker shapes ( p > 0.3), confirming that swarm localization is anchored to marker presence rather than to its specific shape. Global kinematics showed overlapping distributions among marker shapes (q = 0.75–0.92). In contrast, marker geometry significantly influenced swarm horizontal dispersion (q < 0.001) and inter-saccade displacement along both horizontal axes (q < 0.05 and q < 0.001), with marker width along the N-S axis predicting swarm dispersion along the same axis ( p < 0.01, effect size = 0.226). This study shows that visual ground cues shape swarm organization at two levels: marker presence sets swarm location, while marker width controls individual turning distances.