September 12, 2003: Volume 59, Number 1

Catching up with the dragonflies

The dragonfly, it turns out, is one of the most accurate prey capturers in nature, and one of the best fliers too.

In an instant, it darts from a perch atop a cattail to intercept a tiny insect – the mosquito – for a quick meal.

So you can imagine how difficult it is for researchers like Prof. Rob Olberg and his students Rebecca Seaman '04 and Jon Jackson '04 to capture the predators on film.

This summer, in the southwest corner of the Science and Engineering Courtyard, they set up a "Dragonfly Flight Cage," a contraption that looks a lot like one of those screen gazebos favored by the lakeside party set. But inside is a miniature ecosystem complete with a pond (read: kiddie pool) and an assortment of vegetation that comes natural to Odonoatarium.

The researchers tempt the fliers with tiny glass beads that resemble a mosquito, and record the action on high-speed video. Back in the lab, they analyze the footage, paying special attention to head motion before and after it catches its food. Their goal: learn as much as possible about how the dragonfly can so effectively catch food in mid-air.

The project is supported by a grant from the National Science Foundation.

Olberg notes that the experiment went well, except that they had to change test subjects every few days. Besides being great predators, the dragonfly, it turns out, can learn a thing or two about glass beads and researchers.

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