The Secret Lives of Wild Animals — Text-only | Flash Special Report
Large-scale insect migrations have been noted since biblical times, and recently, major progress has been made in understanding how and why hoards of insects move from one geographic location to another. But now, scientists have successfully tracked the migration of individual insects in an effort to learn more about the factors affecting their movements.
The studies pioneer a new era of migration research that takes advantage of miniaturized radio transmitters. In the future, signals from these and similar devices could be detected by satellites. So, small birds, bats and insects could be tracked over continental distances, which would allow better studies of disease transmission and new strategies to control migrating insects that are considered to be pests.
In one example, researchers developed the tiny transmitters and attached them to wild Green Darner dragonflies using a mixture of eyelash adhesive and superglue. After verifying the transmitters did not alter the insects’ flight characteristics, the team tracked the dragonflies as they migrated south from northern New Jersey during the fall months. Each individual was tracked for the life of the transmitter—about seven days.
Scientists surmise that by migrating and laying eggs in more southerly ponds, the Green Darner’s offspring can emerge earlier the following spring and then migrate north to occupy ponds that are still too cold to allow local dragonflies to emerge.
Like migrating songbirds, the dragonflies would travel some days—generally every third day—and rest on other days. When on the move, they flew an average of 7.5 miles per day; one intrepid flier logged an astounding 100 miles in one day!
Winds on flying days blew less than 15 mph. A flying day always followed a night that was colder than the previous night—a sign of a prevailing cold front in which winds blow generally from the north. That meant the dragonflies often took advantage of tailwinds as they made their way south.
1. Using miniature tracking devices, scientists found that Green Darner dragonflies migrate similarly to songbirds. They traveled an average of 7.5 miles per day—moving some days and resting on others, depending on the weather. Credit: Dave McShaffrey, Marietta College
2. Researchers recently tracked individual Green Darner dragonflies as they migrated south from northern New Jersey during the fall months by attaching miniature radio transmitters to them. The tiny beacons, which weigh about as much as a paper clip, were affixed to the dragonflies using a mixture of eyelash adhesive and superglue.
Credit: Christian Ziegler