[MUSIC] Researchers use many different techniques to study various aspects of insect flight, the cues that insects respond to in flight, and the factors that influence their dispersal capacity are important aspects of their ecology. In order to manage insects considered to be pests, factors influencing dispersal capacity and movement behaviors need to be understood. In order to understand small-scale physical mechanisms that power insect flight, researchers examine precise wing movements and deformations that produce lift and alter flight direction. Early techniques to study insect flight were largely qualitative and relied primarily on looking at smoke vertices produced over the wings of tethered insects in flight. From these early studies researchers deduced that lifted insect flight was produced by a leading edge vortex that is created at a fixed point on the wing before spiraling towards the tip. No quantitative measurements could be taken from these experiments, however, and these visualizations represent the flow field in general rather than the flow at any specific instant. More recently, an approach known as digital particle image velocimetry, or DPIV, is used to precisely analyze the flow field around an insect wing. DPIV works by tracking the movement of marker particles using high resolution imaging and recording systems. This instantaneous flow field data can be combined with measurements from an attached strain gauge that measures the forces acting on the insect. This technique allows the development of precise models of flow fields around insect wings, in which the forces and movements of leading edge vertices are accurately incorporated. These experiments allow researchers to understand the small-scale physical mechanisms that powered the movement and dispersal of insects. To understand ecological and physiological factors that influence insect flight, researchers employ tools such as flight mills and wind tunnels. Flight mills allow researchers to identify variables that influence insect dispersal propensity and distance. The insect is tethered to the arm of the mill and allowed to fly under specific conditions over a predetermined period of time. Data collected from computers attached to the flight ills can be used to understand how variables such as insect sex, mating status, body weight, wing size and fat content impact dispersal by flight. As flight on a mill does not accurately replicate dispersal under field conditions, information collected from flight mill bioassays is compared only to other treatments within the study. And does not make predictions about possible dispersal distances in field conditions. Wind tunnels, unlike flight mills, are used to study how insects respond to external cues during flight, such as olfactory or visual stimuli. In wind tunnel bioassays, researchers expose an insect to the test stimulus within the tunnel where its flight patterns are recorded. Wind tunnel experiments provide insights into the cues that flying insects respond to and use for navigation. So there we have it. These are some of the many ways in which researchers can study insect flight. In the next video, we'll move on to some behavioral aspects of flight. You know that wings are important in insect locomotion, but did you know that some insects are capable of migratory flight over vast distances? In the next video we introduce the extraordinary phenomenon of insect migration.