This data is specified at the individual Terrain pages.
|Bog, Fen, Swamp|
How to Acquire
Dragonflies only fly around in swamps!, so you can't run after them, which makes them quite tricky to catch. The easiest way currently is to catch them on horseback, as horses currently move normal speed in a swamp. An alternative method (if you're good at it) is to try and intercept them since their flying pattern is quite clear. Another way is just to right-click and wait, it might take a while but sooner or later you will catch it.
Emerald- versus Ruby-Dragonfly Curiosity data
(More curiosity data available at Curiosity Tables)