Flying insects have evolved the ability to evade looming objects such as predators and swatting hands. This is particularly relevant for blood-feeding insects like mosquitoes that routinely need to evade defensive actions of their blood-hosts. To minimize the chance of being swatted, a mosquito can use two distinct strategies: continuously exhibit an unpredictable flight path or maximize its escape manoeuvrability. We studied how baseline flight unpredictability and escape manoeuvrability affects the escape performance of day-active and night-active mosquitoes (Aedes aegypti and Anopheles coluzzii, respectively). We used a multi-camera high-speed videography system to track how freely flying mosquitoes respond to an event-triggered rapidly approaching mechanical swatter, in four light conditions ranging from pitch darkness to overcast daylight. Results show that both species exhibit enhanced escape performance in their respective natural light condition (daylight for Aedes and dark for Anopheles). To achieve this, they show strikingly different behaviours. The enhanced escape performance of Anopheles at night is explained by their baseline unpredictable erratic flight behaviour, whereas the increased escape performance of Aedes in overcast daylight is due to their enhanced escape manoeuvres. This shows that both day and night active mosquitoes modify their flight behaviour in function of light intensity such that their escape performance is maximum in their natural blood-feeding light conditions, when these defensive actions by their blood-hosts occur most. Because Aedes and Anopheles mosquitoes are major vectors of several deadly human diseases, this knowledge can be used to optimize vector control methods for these specific species.

Database S1: flight tracks of all Anopheles coluzzii and Aedes aegypti mosquitoes attacked by the (virtual) mechanical swatter, and flying in various light conditions. Related to STAR Methods. Two Matlab .mat files contain three-dimensional tracks of all flying mosquitoes (one .mat for each species), described as the time t (s) and the spatial {x, y, z} (m) coordinates of the mosquito at each video frame. The coordinates are in meters, and in the world reference frame as defined in figure 1, with z oriented vertically up, and the origin of the coordinate frame at the centre of the flight arena. The trajectories were determined as described in the materials and methods. Metadata for each track includes species, age, swatter type (black or clear mesh) and mode (on or off), light condition, as well as temperature and humidity over time in the arena during each experiment. In addition, the file contains the kinematic of the mechanical swatter, as well as the geometry of the flight arena and the swatter.

Methods S1: Analysis codes. Related to STAR Methods. Contains all original matlab codes that were written to perform the analysis of the article and to generated the panels of Fig. 1-7. Also contains JAGS modeling codes used for determining the Bayesian generalized linear models (B-GLM) in Fig. 2, 4-7. And codes used for estimating means in Fig. 2 and 7.