Dragonflies Embark on
an Epic Migration Each Year
G'day folks,
As a photographer, I'm always checking out wildlife, and these cute little things are another example of how amazing nature is. Monarch
butterflies aren’t the only migratory marathoners in North America.
The green darner dragonfly, Anax junius, embarks on a rigorous, multi-generational migratory relay race up and down North America every year that largely goes unnoticed, according to a new study published in the journal Biology Letters.
Dragonfly experts knew that the common
emerald green and blue insects migrated, but tracking the jet-setting three-inch-long insect is tricky. The slender insects
are too small for radio trackers and don’t travel in easy-to-spot swarms like
monarchs or birds. To bring the details of the dragonfly’s journey to light,
researchers consulted 21 years of data collected by citizen scientists and
analyzed more than 800 green darner wing samples collected over the last 140
years from museums, reports Susan Milius at Science News.
The team tested each wing sample for a
chemical code that would indicate approximately where the bugs were born. From
there, the researchers could figure out how far the dragonflies travelled as
adults. To do so, they tested for three hydrogen isotopes—or chemical
signatures—each of which vary geographically. Hydrogen accumulates in dragonfly
larvae’s chitin, which is the stuff that eventually makes up their wings as
adults. Identifying the isotope in each wing sample allowed researchers to
narrow in on the dragonflies’ origin. The isotopes aren’t perfect, but they’re
good enough to tell whether they originate in “Florida, Maryland or Maine,”
reports Ben Guarino at The Washington Post.
The citizen science data allowed the
team to figure out what types of natural cues, like temperature, give the
dragonfly larvae the signal to emerge and migrate. Between February and March,
the first generation of dragonflies emerges from ponds and lakes in the
southern United States, Mexico and the Caribbean. Then those resilient
first-gen bugs travel hundreds of miles north as, making it to New England or
the upper Midwest by May. When they get there, they’ll lay their eggs and die.
The lives of the next generation are just as incredible. While some of those second generation insects will hang out and over winter in ponds and lakes in the north during their nymph stage, many will reach maturity and head south between July and October.
When those insects reach the south, they
deposit another batch of eggs, which mature into a third generation that will
live a non-migratory life over the winter on the coast, producing the eggs of
the dragonflies that will migrate northward again in the spring.
“We know that a lot of insects migrate,
but we have full life history and full migration data for only a couple. This
is the first dragonfly in the Western Hemisphere for which we know this,”
senior author of the paper Colin Studds of the University of Maryland,
Baltimore County, says in a press release. “We’ve solved the first piece of a big
mystery.”
The bigger part of the mystery—and one
that applies to migrating butterflies and even birds—is how the insects know
what path to take north and south and when they know to migrate. The data
suggest that the insects begin migrating north once temperatures reach 48
degrees, Studds tells Guarino at The Washington Post. This may also
happen because the days start to grow longer during this time as well.
Clancy's comment: Yep, nature keeps reminding us that we humans are not the smartest things on earth.
I'm ...
