from the phrase "flutter by"--it's a Spoonerism.
Answer: We have not been able to find a definitive answer to this question. One interesting theory about its origin, however, can be found in a book written by Eden Emanuel Sarot in 1958 entitled Folklore of the Dragonfly: A Linguistic Approach. He theorized that the name dragonfly actually came about because of an ancient Romanian Folktale. In the folktale, the Devil turned a beautiful horse ridden by St. George (of St. George and the dragon fame) into a giant, flying insect. The Romanian names the people supposedly refed to this giant insect (when translated into English) mean 'St. George's Horse' or, more commonly, 'Devil's Horse.' According to Sarot, the peasantry of that time actually viewed the Devil's Horse as a giant fly and that they may have started referring to it as the 'Devil's Fly' (instead of Devil's Horse). He stated that the Romanian word for Devil was "drac," but that drac was also the Romanian word for dragon. He thought that eventually the Romanian name for the Devil's Fly was erroneously translated to the English Dragon Fly and this eventually evolved into the "dragonfly!"
they saw a dragon flying
The scientific name for dragonflies is Odonata.
There are several Families of dragonflies. If you are looking for the commonly used general classification name for them, the Order name for dragonflies and damselflies is Odonata. The Suborder for dragonflies is Anisoptera. Odonata Central (http://www.odonatacentral.org) has lots of photos and classification information if you are looking for the Family name for a particular type of dragonfly.
they saw a dragon flying
yes dragoferosus
Dragonflies have too many predators to list. They're eaten by birds, bats, frogs, fish, large spiders, wasps and other dragonflies, to name a few.
Libellula lydia
yes
Odonata is the name of the order of dragonflies. It merges as members insects of the Anisoptera suborder of dragonflies and the Zygoptera suborder of damselflies. The name of the order traces its origins back to the ancient Greek οδόντoς (οδούς, odontos) for "tooth" even though damselflies and dragonflies are not unique in claiming toothed mandibles.
The scientific name for the Blue dasher is Pachydiplax longipennis
Dragonflies do not emit light. The insect that you are thinking of is a firefly, or the scientific name is Lampyridae, which are a class of beetles. They are nicknamed 'lightning bugs' in the US.
Dragonflies are invertebrates
The ancestors to the dragonflies was the Protondonata. These were the 1st winged insects on Earth and the earliest form of dragonflies.