Sundews have usually two glands. Stalked glands produces the sticky glue that captures insects. When the insects land on the sundew, they become stuck and tries to escape. The more they struggle, the more stuck they become and slowly they will die out of exhaustion or when the sticky dew covers their breathing holes.
sooooo coooolllll......
After that, then the sessile glands kick in. These glands produces digestive enzymes that slowly dissolve the insect that was ensnared. The result can be quite horrifying (but I think it is cool
), sometimes, you can see the digestive enzymes drooling from the leaf of the sundew.
Retentive glands are special glands that makes movement. For every sundew, there are many different speeds of movement. Some like drosera spathulata moves only their stalked glands and a little of their tentacles. Others like drosera burmanii and drosera regia moves their tentacles in a dramatic way. Drosera burmanii can move its tentacles in about one minute...........
http://en.wikipedia.org/wiki/Drosera
Try checking this link.
Cheers