Dragonflies are insects with long-standing history, according to some fossil records, it appeared on the Earth about 250 millions years ago. Nowadays, nearly 6,000 species of dragonflies stay alive. They distribute worldwide except in Antarctica. Dragonfly belongs to Order Odonata of Class Insecta. It can be divided into suborders Anisoptera, Zygoptera and Anisozygoptera, the latter one can only be found in Japan and the Himalayas.

General speaking, "Dragonfly" is the collective name for 2 types of insect with similar appearance and behaviours, they are dragonfly (Anisoptera) and damselfly (Zygoptera). Both of them are aggressive carnivores. Their life history pass through 3 stages: egg, naiad and adult (incomplete metamorphsis).

Up to April 2009, there are 115 species of dragonfly officially recorded in Hong Kong, of which, 46 of them have been recorded in Hong Kong Wetland Park.