Dragonflies can be seen flying over rice paddies and rivers with the approach of summer.
Their bodies measure around 5 centimeters and have an overall orange tinge,
causing them to frequently be mistaken for an immature red dragonfly in Japan.
However, there is no such species as “red dragon.”
The representative red colored dragonfly of autumn is the autumn darter.
However, the autumn darter soon leaves for plateau country after metamorphosing into an adult,
and disappears from rice paddies and other low-lying land.
The autumn darter is susceptible to heat and spends the summer in the highlands at altitudes of around 1000 meters.
It then tends to form groups once the autumnal rain front has passed, descending on low-lying land to lay its eggs.
There is, therefore, a good chance that red colored dragonflies spotted over fields in midsummer are not autumn darters.
Other species collectively referred to as a red dragonflies are the summer darter which displays similar behavior to autumn darters but stays in low-lying country during summer, and the most observable species in Europe, the common darter.
But it is the wandering glider that has received special attention in recent years.
While it is virtually impossible to tell these species of dragonfly apart in-flight as they have extremely similar features,
they can be successfully distinguish by identifying their chest and wing patterns when they are stationary.
Although native to tropical regions, the wandering glider can also be seen in eastern Japan.
This species is so widespread in Kyushu and the Kii peninsula that if you see an orangey dragonfly by the water in midsummer in these regions,
you can be sure it is the wandering glider without having to catch it for inspection.
However, the ecology of the wandering glider has some extraordinary aspects.
The wandering glider appears very early in the year,
and can be seen flying in mid-march in Okinawa.
Wandering gliders then mature one after the other,
forming a group that crosses the ocean to lay eggs in the early rice paddies of Kyushu.
Larvae that hatch here grow at incredible speeds to metamorphose in the short period of a month and continue their journey further north.
Most wandering gliders seen at the end of summer in eastern Japan and the Kii peninsula are individuals that metamorphosed in Japan before the rainy season that year.
The wandering glider has a special sensor at the base of its back wings that automatically stops them flapping when an updraft is detected to save energy on long distance flights across the ocean.
However, as the wandering glider’s eggs and larvae cannot develop in temperatures below 10 degrees Celsius,
they can't reproduce even after traveling as far as Kyushu or the Kii peninsula.
This increase in sightings in eastern Japan of the wandering glider,
a species native to tropical regions, is another indication of global warming.
Even so, the biggest mystery is the fact that we know nothing of where the wandering gliders that come to Kyushu every year are metamorphosing.
Wandering gliders somewhere to the south detect a rise in temperature and fly across the ocean to Japan every year taking full advantage of their updraft sensor.
Humans do not have such refined sensors with which to measure the natural world.
However, humankind posses the power of analysis, one that goes beyond our natural limitations.
The protection of this diverse and beautiful earth through the analysis of nature is a mission that has been entrusted to humankind.