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hubie [soylentnews.org] writes:

As far as insect flight goes, landings can be very complicated. Successful landings require matching the relative speed of the target, which could be static like a wall, or moving like a flower in the breeze. The insect must execute complicated coordinated maneuvers based on visual, thermal, acoustic, and olfactory signals. These landings occur over a range of velocities and surface types. Mosquitoes need to manage all of this and land softly enough that the host can't feel them.

One major difference between flying insects and vertebrates is that insects have immobile eyes with fixed focal lengths which prevents them from utilizing stereoscopic vision to judge distances, so they have to rely on image motion such as changes in object size. Different insects have different techniques: honeybees come to a hover 16 mm from a surface before initiating touchdown; houseflies approach objects at constant velocity and once the object reaches a certain relative size on its retina, it decelerates, pitches the body and extends its legs; and fruit flies accelerate towards their landing, extend their legs, and stick the landing like a gymnast with nearly instant deceleration. Mosquitoes have much less mass than a honeybee, but much more mass than a fruit fly, so their landing dynamics were expected to be much different.

Researchers from the University of Central Florida set up an experiment to monitor mosquito flight and landing. They used a high-speed camera and filmed mosquito landings and extracted the physical dynamics using the Open Source Physics Tracker [compadre.org] software. Their results, which are published in a Nature Scientific Reports article [nature.com], found that mosquitoes typically careen in for a head-first landing, they make initial conact with their proboscis before making contact with their legs, then their legs act as underdamped springs resulting in one or two bounces before they come to rest. They determined that the mosquitoes strike the surface with an impact velocity about half of what is perceptible by humans.

The paper provides entertaining slow motion videos [nature.com].

Smith, N.M., Balsalobre, J.B., Doshi, M. et al. Landing mosquitoes bounce when engaging a substrate. Sci Rep 10, 15744 (2020). https://doi.org/10.1038/s41598-020-72462-0 [doi.org]

Abstract
In this experimental study we film the landings of Aedes aegypti mosquitoes to characterize landing behaviors and kinetics, limitations, and the passive physiological mechanics they employ to land on a vertical surface. A typical landing involves 1–2 bounces, reducing inbound momentum by more than half before the mosquito firmly attaches to a surface. Mosquitoes initially approach landing surfaces at 0.1–0.6 m/s, decelerating to zero velocity in approximately 5 ms at accelerations as high as 5.5 gravities. Unlike Dipteran relatives, mosquitoes do not visibly prepare for landing with leg adjustments or body pitching. Instead mosquitoes rely on damping by deforming two forelimbs and buckling of the proboscis, which also serves to distribute the impact force, lessening the potential of detection by a mammalian host. The rebound response of a landing mosquito is well-characterized by a passive mass-spring-damper model which permits the calculation of force across impact velocity. The landing force of the average mosquito in our study is approximately 40 μN corresponding to an impact velocity of 0.24 m/s. The substrate contact velocity which produces a force perceptible to humans, 0.42 m/s, is above 85% of experimentally observed landing speeds.

Original Submission