Enlarge / It may not look special, but it's a radar sensitive enough to track an insect in flight. (credit: Rothamsted Visual Communications Unit)

Researchers in the UK have turned some highly specialized radar equipment to the skies to track a staggering volume of material—3.2 kilotons of it—as it transits the skies of southern England. The material in question? Insects, about 3.5 trillion of them each year. While smaller insects seem to drift on the prevailing wind, larger ones appear to undergo a directed, seasonal migration.

The study relied on a combination of high-tech and old-fashioned hardware, shown above and below. The old-fashioned equipment was a traditional insect-catching net, albeit one that was sent aloft trailing below a miniature blimp. This was needed to pick up smaller insects—below 10mg in body mass—which couldn't be tracked using the radar. The radar was a special piece of equipment, called a vertical-looking entomological radar.

It's impressive hardware. For anything above 10mg, the radar could record "body mass, flight altitude, aerial density, displacement speed, displacement direction, and flight heading." The equipment could do all this up to about 1.2km in altitude, allowing it to catch any high-flying insects. The equipment was set up in three locations in the southern UK and sampled the movement of insects for a full decade to produce the data analyzed in this new paper. During that time, the radars tracked more than 1.8 million individual insects, which were used to extrapolate general trends.

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