WIKIPEDIA : Dragonfly (EN)
In Japan dragonflies are symbols of courage, strength, and happiness, and they often appear in art and literature, especially haiku. In ancient mythology, Japan was known as Akitsushima, which means "Land of the Dragonflies". The love for dragonflies is reflected by the fact that there are traditional names for almost all of the 200 species of dragonflies found in and around Japan.[7] Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.[8]
Also, in Japan, amongst the Three Great Spears of Japan is one which is called the Tonbo-giri, which when translated is called 'The Dragon Fly Cutter'. The spear is an important part of Japans imperial regalia- the spear itself was once wielded by the legendary Samurai, Honda Tadakatsu. It's name is derived from the story that the blade is so sharp, a dragon fly once landed on it and was instantly cut in half.

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http://en.wikipedia.org/wiki/Dragonfly